Quarter Wit, Quarter Wisdom: Solving GMAT Critical Reasoning Questions Involving Rates

Quarter Wit, Quarter WisdomIn our “Quarter Wit, Quarter Wisdom” series, we have seen how to solve various rates questions – the basic ones as well as the complicated ones. But we haven’t considered critical reasoning questions involving rates, yet. In fact, the concept of rates makes these problems very difficult to both understand and explain. First, let’s look at what “rate” is.

Say my average driving speed is 60 miles/hr. Does it matter whether I drive for 2 hours or 4 hours? Will my average speed change if I drive more (theoretically speaking)? No, right? When I drive for more hours, the distance I cover is more. When I drive for fewer hours, the distance I cover is less. If I travel for a longer time, does it mean my average speed has decreased? No. For that, I need to know  what happened to the distance covered. If the distance covered is the same while time taken has increased, only then can I say that my speed was reduced.

Now we will look at an official question and hopefully convince you of the right answer:

The faster a car is traveling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars.

Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?

(A) The average number of passengers per car on highways increased.

(B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.

(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another.

(D) The average mileage driven on highways per car increased.

(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.

Let’s break down the given argument:

  • The faster a car, the higher the risk of fatality.
  • In a span of 5 years, the average highway speed has increased.
  • In the same time, the number of car crash fatalities per highway mile driven by cars has reduced.

This is a paradox question. In last 5 years, the average highway speed has increased. This would have increased the risk of fatality, so we would expect the number of car crash fatalities per highway mile to go up. Instead, it actually goes down. We need to find an answer choice that explains why this happened.

(A) The average number of passengers per car on highways increased.

If there are more people in each car, the risk of fatality increases, if anything. More people are exposed to the possibility of a crash, and if a vehicle is in fact involved in an accident, more people are at risk. It certainly doesn’t explain why the rate of fatality actually decreases.

(B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.

This option tells us that the safety features in the cars have been enhanced. That certainly explains why the fatality rate has gone down. If the cars are safer now, the risk of fatality would have reduced, hence this option does help us in explaining the paradox. This is the answer, but let’s double-check by looking at the other options too.

(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another.

This option is irrelevant – why the average speed increased is not our concern at all. Our only concern is that average speed has, in fact, increased. This should logically increase the risk of fatality, and hence, our paradox still stands.

(D) The average mileage driven on highways per car increased.

This is the answer choice that troubles us the most. The rate we are concerned about is number of fatalities/highway mile driven, and this option tells us that mileage driven by cars has increased.

Now, let’s consider the parallel with our previous distance-rate-time example:

Rate = Distance/Time

We know that if I drive for more time, it doesn’t mean that my rate changes. Here, however:

Rate = Number of fatalities/highway mile driven

In this case, if more highway miles are driven, it doesn’t mean that the rate will change. It actually has no impact on the rate; we would need to know what happened to the number of fatalities to find out what happened to the rate. Hence this option does not explain the paradox.

(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.

This answer choice tells us that on average, the trips were made more quickly, i.e. the speed increased. The given argument already tells us that, so this option does not help resolve the paradox.

Our answer is, therefore, (B).

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTubeGoogle+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Kanye, Wiz Khalifa, Twitter Beef…and GMAT Variables

GMAT Tip of the WeekThis week, the internet exploded with a massive Twitter feud between rappers Kanye West and Wiz Khalifa, with help from their significant others and exes. For days now, hashtags unpublishable for an education blog have topped the trending lists, all as a result of the epic social media confrontation. And all of THAT originated from a classic GMAT mistake from the Louis Vuitton Don – a man who so loves his hometown Kellogg School of Management that he essentially named his daughter Northwestern – himself:

Kanye didn’t consider all the possibilities when he saw variables.
A brief history of the beef: there was musical origin, as Wiz wanted a bit of credit for his young/wild/free friends for the term “Wave,” as Kanye changed his upcoming album title from Swish to Waves. But where things escalated quickly all stemmed from Wiz’s use of variables in the following tweet:

Hit this kk and become yourself.

Kanye, whose wife bears those exact initials, K.K., immediately interpreted those variables as a reference to Kim and lost his mind. But Wiz had intended those variables kk to mean something entirely different, a reference to his favorite drug of choice. And then…well let’s just say that things got out of hand.

So back to the GMAT: Kanye’s main mistake was that he didn’t consider alternate possibilities for the variables he saw in the tweet, and quickly built in some incorrect assumptions that led to disastrous results. Do not let this happen to you on the GMAT! Here’s how it could happen:

1) Forgetting about not-obvious numbers.
If a problem, for example, defines k as 10 < k < 12, you can’t just think “k = 11” because you don’t know that k has to be an integer. 11.9 or 10.1 are also possibilities. Similarly if k^2 = 121, you have to consider that k could be -11 as well as it could be 11.

Ultimately, that was Yeezy’s mistake: he saw KK and with tunnel vision saw the most obvious possibility. But why couldn’t “KK” have been Krispy Kreme or Kyle Korver or Kato Kaelin? Before you leap to conclusions on a GMAT variable, see if there’s anything else it could be.

2) Assuming that each variable must represent a different number.
This one is a bit more nuanced. Suppose you were asked:

For positive integers a and b, is the product ab > 1?

(1) a = 1

With that statement, you might start thinking, “Well if a is 1, b has to be something else…” but all the variable b really means is “a number we don’t know.” Just because a problem assigns two different variables does not mean that they represent two different numbers! B could also be 1…we just don’t know yet.

Where this manifests itself as a problem most often is on function problems. When people see the setup, for example:

The function f is defined for all values x as f(x) = x^2 – x – 1

They’ll often be confused when that’s paired with a question like, “Is f(a) > 1?” and a statement like:

(1) -2 < a < 2

“I know about f(x) but I don’t know anything about f(a),” they might say, but the way these variables work, f(x) means “the function of any number…we just don’t know which number” so when you then see f(a), a becomes that number you don’t know. You’ll do the same thing for a: f(a) = a^2 – a – 1. What goes in the parentheses is just “the number you perform the function on” – the function doesn’t just apply to the variable in the definition, but to any number, variable, or combination that is then put in the parentheses.

The real lesson here is this: variables on the GMAT are a lot like variables in Wiz Khalifa’s Twitter feed. You might think you know what they mean, but before you stake your reputation (or score) on your response to those variables, consider all the options. Hit this GMAT and become yourself.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTubeGoogle+ and Twitter!

By Brian Galvin.

Why Logic is More Important Than Algebra on the GMAT

QuestioningOne common complaint I get from students is that their algebra skills aren’t where they need to be to excel on the GMAT. This complaint, invariably, is followed by a request for additional algebra drills.

If you’ve followed this blog for any length of time, you know that one of the themes we stress is that Quantitative Reasoning is not, primarily, a math test. Though math is certainly involved – How could it not be? – logic and reasoning are far more important factors than conventional mathematical facility. I stress this in every class I teach. So why the misconception that we need to hone our algebra chops?

I suspect that the culprit here is the explanations that often accompany official GMAC questions. On the whole, they tend to be biased in favor of purely algebraic solutions.  They’re always technically correct, but often suboptimal for the test-taker who needs to arrive at a solution within two minutes. Consequently, many students, after reviewing these solutions and arriving at the conclusion that they would not have been capable of the hairy algebra proffered in the official solution, think they need to work on this aspect of their prep. And for the most part it isn’t true.

Here’s a good example:

If x, y, and k are positive numbers such that [x/(x+y)]*10 + [y/(x+y)]*20 = k and if x < y, which of the following could be the value of k? 

A) 10
B) 12
C) 15
D) 18
E) 30

A large percentage of test-takers see this question, rub their hands together, and dive into the algebra. The solution offered in the Official Guide does the same – it is about fifteen steps, few of them intuitive. If you were fortunate enough to possess the algebraic virtuosity to solve the question in this manner, you’d likely chew up 5 or 6 minutes, a disastrous scenario on a test that requires you to average 2 minutes per problem.

The upshot is that it’s important for test-takers, when they peruse the official solution, not to arrive at the conclusion that they need to solve this question the same way the solution-writer did. Instead, we can use the same simple strategies we’re always preaching on this blog: pick some simple numbers.

We’re told that x<y, but for my first set of numbers, I like to make x and y the same value – this way, I can see what effect the restriction has on the problem. So let’s say x = 1 and y = 1. Plugging those values into the equation, we get:

(1/2) * 10 + (1/2) * 20  = k

5 + 10 = k

15 = k

Well, we know this isn’t the answer, because x should be less than y. So scratch off C. And now let’s see what the effect is when x is, in fact, less than y. Say x = 1 and y = 2. Now we get:

(1/3) * 10 + (2/3) * 20  = k

10/3 + 40/3 = k

50/3 = k

50/3 is about 17. So when we honor the restriction, k becomes larger than 15. The answer therefore must be D or E. Now we could pick another set of numbers and pay attention to the trend, or we can employ a bit of logic and common sense. The first term in the equation x/(x+y)*10 is some fraction multiplied by 10. So this term, logically, is some value that’s less than 10.

The second term in the equation is y/(x+y)*20, is some fraction multiplied by 20, this term must be less than 20. If we add a number that’s less than 10 to a number that’s less than 20, we’re pretty clearly not going to get a sum of 30. That leaves us with an answer of 18, or D.

(Note that if you’re really savvy, you’ll recognize that the equation is a weighted average. The coefficients in the weighted average are 10 and 20. If x and y were equal, we’d end up at the midway point, 15. Because 20 is multiplied by y, and y is greater than x, we’ll be pulled towards the high end of the range, leading to a k that must fall between 15 and 20 – only 18 is in that range.)

Takeaway: Never take a formal solution to a problem at face value. All you’re seeing is one way to solve a given question. If that approach doesn’t resonate for you, or seems so challenging that your conclusion is that you must purchase a host of textbooks in order to improve your formal math skills, then you haven’t absorbed what the GMAT is really about. Often, the relevant question isn’t, “Can you do the math?” It’s, “Can you reason your way to the answer without actually doing the math?”

*Official Guide question courtesy of the Graduate Management Admissions Council.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Quarter Wit, Quarter Wisdom: Should You Use the Permutation or Combination Formula?

Quarter Wit, Quarter WisdomA recurring question from many students who are preparing for GMAT is this: When should one use the permutation formula and when should one use the combination formula?

People have tried to answer this question in various ways, but some students still remain unsure. So we will give you a rule of thumb to follow in all permutation/combination questions:

You never NEED to use the permutation formula! You can always use the combination formula quite conveniently. First let’s look at what these formulas do:

Permutation: nPr = n!/(n-r)!
Out of n items, select r and arrange them in r! ways.

Combination: nCr = n!/[(n-r)!*r!]
Out of n items, select r.

So the only difference between the two formulas is that nCr has an additional r! in the denominator (that is the number of ways in which you can arrange r elements in a row). So you can very well use the combinations formula in place of the permutation formula like this:

nPr = nCr * r!

The nCr formula is far more versatile than nPr, so if the two formulas confuse you, just forget about nPr.

Whenever you need to “select,” “pick,” or “choose” r things/people/letters… out of n, it’s straightaway nCr. What you do next depends on what the question asks of you. Do you need to arrange the r people in a row? Multiply by r!. Do you need to arrange them in a circle? Multiply by (r-1)!. Do you need to distribute them among m groups? Do that! You don’t need to think about whether it is a permutation problem or a combination problem at all. Let’s look at this concept more in depth with the use of a few examples.

There are 8 teachers in a school of which 3 need to give a presentation each. In how many ways can the presenters be chosen?

In this question, you simply have to choose 3 of the 8 teachers, and you know that you can do that in 8C3 ways. That is all that is required.

8C3 = 8*7*6/3*2*1 = 56 ways

Not too bad, right? Let’s look at another question:

There are 8 teachers in a school of which 3 need to give a presentation each. In how many ways can all three presentations be done?

This question is a little different. You need to find the ways in which the presentations can be done. Here the presentations will be different if the same three teachers give presentations in different order. Say Teacher 1 presents, then Teacher 2 and finally Teacher 3 — this will be different from Teacher 2 presenting first, then Teacher 3 and finally Teacher 1. So, not only do we need to select the three teachers, but we also need to arrange them in an order. Select 3 teachers out of 8 in 8C3 ways and then arrange them in 3! ways:

We get 8C3 * 3! = 56 * 6 = 336 ways

Let’s try another one:

Alex took a trip with his three best friends and there he clicked 7 photographs. He wants to put 3 of the 7 photographs on Facebook. How many groups of photographs are possible?

For this problem, out of 7 photographs, we just have to select 3 to make a group. This can be done in 7C3 ways:

7C3 = 7*6*5/3*2*1 = 35 ways

Here’s another variation:

Alex took a trip with his three best friends and there he clicked 7 photographs. He wants to put 3 of the 7 photographs on Facebook, 1 each on the walls of his three best friends. In how many ways can he do that?

Here, out of 7 photographs, we have to first select 3 photographs. This can be done in 7C3 ways. Thereafter, we need to put the photographs on the walls of his three chosen friends. In how many ways can he do that? Now there are three distinct spots in which he will put up the photographs, so basically, he needs to arrange the 3 photographs in 3 distinct spots, which that can be done in 3! ways:

Total number of ways = 7C3 * 3! = (7*6*5/3*2*1) * 6= 35 * 6 = 210 ways

Finally, our last problem:

12 athletes will run in a race. In how many ways can the gold, silver and bronze medals be awarded at the end of the race?

We will start with selecting 3 of the 12 athletes who will win some position in the race. This can be done in 12C3 ways. But just selecting 3 athletes is not enough — they will be awarded 3 distinct medals of gold, silver, and bronze. Athlete 1 getting gold, Athlete 2 getting silver, and Athlete 3 getting bronze is not the same as Athlete 1 getting silver, Athlete 2 getting gold and Athlete 3 getting bronze. So, the three athletes need to be arranged in 3 distinct spots (first, second and third) in 3! ways:

Total number of ways = 12C3 * 3! ways

Note that some of the questions above were permutation questions and some were combination questions, but remember, we don’t need to worry about which is which. All we need to think about is how to solve the question, which is usually by starting with nCr and then doing any other required steps. Break the question down — select people and then arrange if required. This will help you get rid of the “permutation or combination” puzzle once and for all.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTubeGoogle+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Stay In Your Lane (In The Snow And On Sentence Correction)

GMAT Tip of the WeekAs the east coast braces for a historic winter storm (and Weezer fans can’t get “My Name is Jonas” out of their heads), there’s a lesson that needs to be taught from Hanover to Cambridge to Manhattan to Philadelphia to Charlottesville.

When driving in the snow:

  • Don’t brake until you have to.
  • Don’t make sudden turns or lane changes, and only turn if you have to.
  • Stay calm and leave yourself space and time to make decisions.

And those same lessons apply to GMAT Sentence Correction. Approach these questions like you would approach driving in a blizzard, and you may very well earn that opportunity to drive through blustery New England storms as you pursue your MBA. What does that mean?

1) Stay In Your Lane
Just as quick, sudden jerks of the steering wheel will doom you on snowy/icy roads, sudden and unexpected decisions on GMAT Sentence Correction will get you in trouble. Your “lane” consists of the decisions that you’ve studied and practiced and can calmly execute: Modifiers, Verbs (tense and agreement), Pronouns, Comparisons, Parallelism in a Series, etc. It’s when you get out of that lane that you’re prone to skidding well off track. For example, on this problem (courtesy the Official Guide for GMAT Review):

While Jackie Robinson was a Brooklyn Dodger, his courage in the face of physical threats and verbal attacks was not unlike that of Rosa Parks, who refused to move to the back of a bus in Montgomery, Alabama.

(A) not unlike that of Rosa Parks, who refused
(B) not unlike Rosa Parks, who refused
(C) like Rosa Parks and her refusal
(D) like that of Rosa Parks for refusing
(E) as that of Rosa Parks, who refused

Your “lane” here is to check for Modifiers (Is “who refused” correct? Is it required?) and for logical, clear meaning (it is required, because otherwise you aren’t sure who refused to move to the back of the bus). But examinees are routinely baited into “jerking the wheel” and turning against the strange-but-correct structure of “not unlike.” When you’re taken off of your game, you often eliminate the correct answer (A) because you’re turning into a decision you’re just not great at making.

2) Don’t Turn or Brake Until You Have To
The GMAT does test Redundancy and Pronoun Reference (among other things), but those are error types that are dangerous to prioritize – much like it’s dangerous while driving in snow to decide quickly that you need to turn or hit the brakes. Too often, test-takers will slam on the Sentence Correction brakes at their first hint of, “That’s redundant!” (like they would for “not unlike” above) or “There are multiple nouns – that pronoun is unclear!” and steer away from that answer choice.

The problem, as you saw above, is that often this means you’re turning away from the proper path. “Not unlike” may scream “double-negative” or “redundant” to many, but it’s a perfectly valid way to express the idea that the two things aren’t close to identical, but they’re not as different as you might think. And you don’t need to know THAT, as much as you need to know that you shouldn’t ever make redundancy your first decision, because if you’re like most examinees you’re probably not that great at you…AND you don’t have to be, because the path toward your strengths will get you to your destination.

Similarly, this week the Veritas Prep Homework Help service got into an interesting email thread about why this sentence:

Based on his experience in law school, John recommended that his friend take the GMAT instead of the LSAT.

has a pronoun reference error, but this sentence:

Mothers expect unconditional love from their children, and they are rarely disappointed.

does not. And while there likely exists a technical, grammatical reason why, the GMAT reason really comes down to this: Does the problem make you address the pronoun reference? If not, don’t worry about it. In other words, don’t brake or turn until you have to. If you look at those sentences in GMAT problem form, you might have:

Based on his experience in law school, John recommended that his friend take the GMAT instead of the LSAT.

(A) Based on his experience in law school, John

(B) Having had a disappointing experience in law school, John

(C) Given his experience in law school, John

Here, the question forces you to deal with the pronoun problem. The major differences between the choices are that A and C involve a pronoun, and B doesn’t. Here, you have to deal with that issue. But for the other sentence, you might see:

Mothers expect unconditional love from their children, and they are rarely disappointed.

(A) Mothers expect unconditional love from their children, and they are

(B) The average mother expects unconditional love from their children, and are

(C) The average mother expects unconditional love from their children, and they are

(D) Mothers, expecting unconditional love from their children, they are

Here, the only choice that doesn’t include the pronoun “they” is choice B, but that choice commits a glaring pronoun (and verb) agreement error (“the average mother” is singular, but “their children” is plural…and the verb “are” is, too). So you don’t need to worry about the “they” (which clearly refers to “mothers” and not “children,” even though there happen to be two plural nouns in the sentence).

Grammatically, the presence of multiple nouns doesn’t alone make the pronoun itself ambiguous, but strategically for the GMAT, what you really need to know is that you don’t have to hit the brakes at the first sign of “unclear reference.” Wait and see if the answer choices give you a chance to address that, and if they do, then make sure that those choices are free of other, more binary errors first. Don’t turn or brake unless you have to.

3) Stay calm and leave yourself space to make decisions.
Just like a driver in the snow, as a GMAT test-taker you’ll be nervous and antsy. But don’t let that force you into rash decisions! Assess the answer choices before you try to determine whether something outside your 100% confidence interval is right or wrong in the original. You don’t need to make a decision on Choice A right away, just like you don’t need to change lanes simply for the sake of doing so. Have a plan and stick to it, both on the GMAT and on those snowy roads this weekend.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

Quarter Wit, Quarter Wisdom: Keeping an Open Mind in Critical Reasoning

Quarter Wit, Quarter WisdomToday we will discuss why it is important to keep an open mind while toiling away on your GMAT studying. Don’t go into test day with biases expecting that if a question tells us this, then it must ask that. GMAC testmakers are experts in surprising you and taking advantage of your preconceived notions, which is how they confuse you and convert a 600-level question to a 700-level one.

We have discussed necessary and sufficient conditions before; we have also discussed assumptions before. This question from our own curriculum is an innovative take on both of these concepts. Let’s take a look.

All of the athletes who will win a medal in competition have spent many hours training under an elite coach. Michael is coached by one of the world’s elite coaches; therefore it follows logically that Michael will win a medal in competition.

The argument above logically depends on which of the following assumptions?

(A) Michael has not suffered any major injuries in the past year.

(B) Michael’s competitors did not spend as much time in training as Michael did.

(C) Michael’s coach trained him for many hours.

(D) Most of the time Michael spent in training was productive.

(E) Michael performs as well in competition as he does in training.

First we must break down the argument into premises and conclusions:

Premises:

  • All of the athletes who will win a medal in competition have spent many hours training under an elite coach.
  • Michael is coached by one of the world’s elite coaches.

Conclusion: Michael will win a medal in competition.

Read the argument carefully:

All of the athletes who will win a medal in competition have spent many hours training under an elite coach.

Are you wondering, “How does one know that all athletes who will win (in the future) would have spent many hours training under an elite coach?”

The answer to this is that it doesn’t matter how one knows – it is a premise and it has to be taken as the truth. How the truth was established is none of our business and that is that. If we try to snoop around too much, we will waste precious time. Also, what may seem improbable may have a perfectly rational explanation. Perhaps all athletes who are competing have spent many hours under an elite coach – we don’t know.

Basically, what this statement tells us is that spending many hours under an elite coach is a NECESSARY condition for winning. What you need to take away from this statement is that “many hours training under an elite coach” is a necessary condition to win a medal. Don’t worry about the rest.

Michael is coached by one of the world’s elite coaches.

It seems that Michael satisfies one necessary condition: he is coached by an elite coach.

Conclusion: Michael will win a medal in competition.

Now this looks like our standard “gap in logic”. To get this conclusion, the necessary condition has been taken to be sufficient. So if we are asked for the flaw in the argument, we know what to say.

Anyway, let’s check out the question (this is usually our first step):

The argument above logically depends on which of the following assumptions?

Note the question carefully – it is asking for an assumption, or a necessary premise for the conclusion to hold.

We know that “many hours training under an elite coach” is a necessary condition to win a medal. We also know that Michael has been trained by an elite coach. Note that we don’t know whether he has spent “many hours” under his elite coach. The necessary condition requires “many hours” under an elite coach.

If Michael has spent many hours under the elite coach then he satisfies the necessary condition to win a medal. It is still not sufficient for him to win the medal, but our question only asks for an assumption – a necessary premise for the conclusion to hold. It does not ask for the flaw in the logic.

Focus on what you are asked and look at answer choice (C):

(C) Michael’s coach trained him for many hours.

This is a necessary condition for Michael to win a medal. Hence, it is an assumption and therefore, (C) is the correct answer.

Don’t worry that the argument is flawed. There could be another question on this argument which asks you to find the flaw in it, however this particular question asks you for the assumption and nothing more.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTubeGoogle+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Your MLK Study Challenge (Remove Your Biases)

GMAT Tip of the WeekAs we celebrate Martin Luther King, Jr. this weekend, you may take some of your free time to study for the GMAT. And if you do, make sure to heed the lessons of Dr. King, particularly as you study Data Sufficiency.

If Dr. King were alive today, he would certainly be proud of the legislation he inspired to end much of the explicit bias – you can’t eat here, vote there, etc. – that was part of the American legal code until the 1960s. But he would undoubtedly be dismayed by the implicit bias that still runs rampant across society.

This implicit bias is harder to detect and even harder to “fix.” It’s the kind of bias that, for example, the movie Freaknomics shows; often when the name at the top of a resume connotes some sort of stereotype, it subconsciously colors the way that the reader of that resume processes the rest of the information on it.

While that kind of subconscious bias is a topic for a different blog to cover, it has an incredible degree of relevance to the way that you attack GMAT Data Sufficiency problems. If you’re serious about studying for the GMAT, you’ll probably have long enacted your own versions of the Voting Rights Act and Civil Rights Act well before you get to test day – that is to say, you’ll have figured out how to eliminate the kind of explicit bias that comes from reading a question like:

If y is an odd integer and the product of x and y equals 222, what is the value of x?

1) x > 0

2) y is a 3 digit number

Here, you’ll likely see very quickly that Statement 1 is not sufficient, and come back to Statement 2 with fresh eyes. You don’t know that x is positive, so you’ll quickly see that y could be 111 and x could be 2, or that y could be -111 and x could be -2, so Statement 2 is clearly also not sufficient. The explicit bias that came from seeing “x is positive” is relatively easy to avoid – you know not to carry over that explicit information from Statement 1 to Statement 2.

But you also need to be just as aware of implicit bias. Try this question, as it is more likely to appear on the actual GMAT:

If y is an odd integer and the product of x and y equals 222, what is the value of x?

1) x is a prime number

2) y is a 3 digit number

On this version of the problem, people become extremely susceptible to implicit bias. You no longer get to quickly rule out the obvious “x is positive.” Here, the first statement serves to pollute your mind – it is, on its own merit, sufficient (if y is odd and the product of x and y is even, the only prime number x could be is 2, the only even prime), but it also serves to get you thinking about positive numbers (only positive numbers can be prime) and integers (only integers are prime). But those aren’t explicitly stated; they’re just inferences that your mind quickly makes, and then has trouble getting rid of. So as you assess Statement 2, it’s harder for you to even think of the possibilities that:

x could be -2 and y could be -111: You’re not thinking about negatives!

x could be 2/3 and y could be 333: You’re not thinking about non-integers!

On this problem, over 50% of users say that Statement 2 is sufficient (and less than 25% correctly answer A, that Statement 1 alone is sufficient), because they fall victim to that implicit bias that comes from Statement 1 whispering – not shouting – “positive integers.”

Harder problems will generally prey on your more subtle bias, so you need to make sure you’re giving each statement a fresh set of available options. So this Martin Luther King, Jr. weekend, applaud the progress that you have made in removing explicit bias from your Data Sufficiency regimen – you now know not to include Statement 1 directly in your assessment of Statement 2 ALONE – but remember that implicit bias is just as dangerous to your score. Pay attention to the times that implicit bias draws you to a poor decision, and be steadfast in your mission to give each statement its deserved, unbiased attention.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

GMAC to Test “Select Section Order” Option

GMAT Select Section Order PilotBig news in the standardized testing space! For a brief period of time starting next month, the Graduate Management Admission Council (GMAC) will let GMAT candidates choose the order in which they take the GMAT. The “Select Section Order Pilot” will run from February 23 through March 8, 2016. The pilot was first announced via an email to candidates who recently took the GMAT, and it appears to be limited to “invitation only” status for some people who recently took the exam.

What Exactly Is The Pilot?
Currently, the GMAT is given one way and one way only: Analytical Writing Assessment (30 minutes), Integrated Reasoning (30 minutes), Quantitative (75 minutes), and Verbal (75 minutes). With the pilot, students may choose to take the GMAT in one of these four ways:

1. Quantitative, Verbal, Integrated Reasoning, Analytical Writing Assessment
2. Quantitative, Verbal, Analytical Writing Assessment, Integrated Reasoning
3. Verbal, Quantitative, Integrated Reasoning, Analytical Writing Assessment
4. Analytical Writing Assessment, Integrated Reasoning, Verbal, Quantitative

You will need to select your preferred order when you register for a new test date on MBA.com. If you choose one of the experimental options above, then you will need to find an available test center in the February 23 – March 8 period; if choose the normal order in which the GMAT is given now (AWA, IR, Quant, Verbal), then you will not be considered part of the pilot program, and you can register for the test on any date.

On its website, GMAC makes a point of saying that the pilot will be very small, involving less than 1% of total testing volume. So, your odds of being invited to the pilot are very small. Also, if you participate, your score will be considered just as valid as if you had taken the “normal” GMAT, and schools will not know that you were part of the Select Section Order pilot.

Why Is GMAC Doing This?
No doubt GMAC wants to innovate and make the GMAT more applicant-friendly in the face of increasing competition from ETS in the form of the GRE. In its email to recent test takers, GMAC wrote:

A launch schedule for any further release of this feature beyond the pilot has not been determined at this time. The wider launch of the Select Section Order feature will depend greatly on the results of the pilot. GMAC may decide not to launch the feature for any number of reasons, including candidate dissatisfaction with the feature.

It’s safe to assume that GMAC will only expand the program if it finds that pilot students don’t perform significantly better or worse than their counterparts who take the GMAT in its normal order. Focusing the test on retake students — who give GMAC a terrific baseline for comparing results between the normal GMAT and the pilot program — is how they will determine whether or not playing with section order has a meaningful impact on scores.

Should You Participate?
If you’re one of the approximately 1% of GMAT candidates who are invited to take part in the pilot, it will be very tempting to take part and try customizing your test day experience. However, we normally recommend that students play the real game just the way they do in practice (and vice versa)… If you’re taking practice tests in the normal order, then we recommend taking the real GMAT the same way.

If stamina is a real problem for you — e.g., you find that you always run out of steam on the Verbal section and start making silly mistakes or simply run out of time — then it may be worth trying a format in which you get Quant and Verbal out of the way first. If you’re not sure, then stick with the normal order that you’re used to.

Were you invited to take part in the pilot? If so, let us know in the comments below!

By Scott Shrum

Quarter Wit, Quarter Wisdom: An Interesting Property of Exponents

Quarter Wit, Quarter WisdomToday, let’s take a look at an interesting number property. Once we discuss it, you might think, “I always knew that!” and “Really, what’s new here?” So let me give you a question beforehand:

For integers x and y, 2^x + 2^y = 2^(36). What is the value of x + y?

Think about it for a few seconds – could you come up with the answer in the blink of an eye? If yes, great! Close this window and wait for the next week’s post. If no, then read on. There is much to learn today and it is an eye-opener!

Let’s start by jotting down some powers of numbers:

Power of 2: 1, 2, 4, 8, 16, 32 …

Power of 3: 1, 3, 9, 27, 81, 243 …

Power of 4: 1, 4, 16, 64, 256, 1024 …

Power of 5: 1, 5, 25, 125, 625, 3125 …

and so on.

Obviously, for every power of 2, when you multiply the previous power by 2, you get the next power (4*2 = 8).

For every power of 3, when you multiply the previous power by 3, you get the next power (27*3 = 81), and so on.

Also, let’s recall that multiplication is basically repeated addition, so 4*2 is basically 4 + 4.

This leads us to the following conclusion using the power of 2:

4 * 2 = 8

4 + 4 = 8

2^2 + 2^2 = 2^3

(2 times 2^2 gives 2^3)

Similarly, for the power of 3:

27 * 3 = 81

27 + 27 + 27 = 81

3^3 + 3^3 + 3^3 = 3^4

(3 times 3^3 gives 3^4)

And for the power of 4:

4 * 4 = 16

4 + 4 + 4 + 4 = 16

4^1 + 4^1 + 4^1 + 4^1 = 4^2

(4 times 4^1 gives 4^2)

Finally, for the power of 5:

125 * 5 = 625

125 + 125 + 125 + 125 + 125 = 625

5^3 + 5^3 + 5^3 + 5^3 + 5^3 = 5^4

(5 times 5^3 gives 5^4)

Quite natural and intuitive, isn’t it? Take a look at the previous question again now.

For integers x and y, 2^x + 2^y = 2^(36). What is the value of x + y?

A) 18

(B) 32

(C) 35

(D) 64

(E) 70

Which two powers when added will give 2^(36)?

From our discussion above, we know they are 2^(35) and 2^(35).

2^(35) + 2^(35) = 2^(36)

So x = 35 and y = 35 will satisfy this equation.

x + y = 35 + 35 = 70

Therefore, our answer is E.

One question arises here: Is this the only possible sum of x and y? Can x and y take some other integer values such that the sum of 2^x and 2^y will be 2^(36)?

Well, we know that no matter which integer values x and y take, 2^x and 2^y will always be positive, which means both x and y must be less than 36. Now note that no matter which two powers of 2 you add, their sum will always be less than 2^(36). For example:

2^(35) + 2^(34) < 2^(35) + 2^(35)

2^(2) + 2^(35) < 2^(35) + 2^(35)

etc.

So if x and y are both integers, the only possible values that they can take are 35 and 35.

How about something like this: 2^x + 2^y + 2^z = 2^36? What integer values can x, y and z take here?

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTubeGoogle+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Make 2016 The Year Of Number Fluency

GMAT Tip of the WeekWhether you were watching the College Football Playoffs or Ryan Seacrest; whether you were at a house party, in a nightclub, or home studying for the GMAT; however you rang in 2016, if 2016 is the year that you make your business school goals come true, hopefully you had one of the following thoughts immediately after seeing the number 2016 itself:

  • Oh, that’s divisible by 9
  • Well, obviously that’s divisible by 4
  • Huh, 20 and 16 are consecutive multiples of 4
  • 2, 0, 1, 6 – that’s three evens and an odd
  • I wonder what the prime factors of 2016 are…

Why? Because the GMAT – and its no-calculator-permitted format for the Quant Section – is a test that highly values and rewards mathematical fluency. The GMAT tests patterns in, and properties of, numbers quite a bit. Whenever you see a number flash before your eyes, you should be thinking about even vs. odd, prime vs. composite, positive vs. negative, “Is that number a square or not?” etc. And, mathematically speaking, the GMAT is a multiplication/division test more than a test of anything else, so as you process numbers you should be ready to factor and divide them at a moment’s notice.

Those who quickly see relationships between numbers are at a huge advantage: they’re not just ready to operate on them when they have to, they’re also anticipating what that operation might be so that they don’t have to start from scratch wondering how and where to get started.

With 2016, for example:

The last two digits are divisible by 4, so you know it’s divisible by 4.

The sum of the digits (2 + 0 + 1 + 6) is 9, a multiple of 9, so you know it’s divisible by 9 (and also by 3).

So without much thinking or prompting, you should already have that number broken down in your head. 16 divided by 4 is 4 and 2000 divided by 4 is 500, so you should be hoping that the number 504 (also divisible by 9) shows up somewhere in a denominator or division operation (or that 4 or 9 does).

So, for example, if you were given a problem:

In honor of the year 2016, a donor has purchased 2016 books to be distributed evenly among the elementary schools in a certain school district. If each school must receive the same number of books, and there are to be no books remaining, which of the following is NOT a number of books that each school could receive?

(A) 18

(B) 36

(C) 42

(D) 54

(E) 56

You shouldn’t have to spend any time thinking about choices A and B, because you know that 2016 is divisible by 4 and by 9, so it’s definitely divisible by 36 which means it’s also divisible by every factor of 36 (including 18). You don’t need to do long division on each answer choice – your number fluency has taken care of that for you.

From there, you should look at the other numbers and get a quick sense of their prime factors:

42 = 2 * 3 * 7 – You know that 2016 is divisible by 2 and 3, but what about 7?

54 = 2 * 3 * 3 * 3 – You know that 2016 is divisible by that 2 and that it’s divisible by 9, so you can cover two of the 3s. But is 2016 divisible by three 3s?

56 = 2 * 2 * 2 * 7 – You know that two of the 2s are covered, and it’s quick math to divide 2016 by 4 (as you saw above, it’s 504). Since 504 is still even, you know that you can cover all three 2s, but what about 7?

Here’s where good test-taking strategy can give you a quick leg up: to this point, a savvy 700-scorer shouldn’t have had to do any real “work,” but testing all three remaining answer choices could now get a bit labor intensive. Unless you recognize this: for C and E, the only real question to be asked is “Is 2016 divisible by 7?” After all, you’re already accounted for the 2 and 3 out of 42, and you’ve already accounted for the three 2s out of 56.

7 is the only one you haven’t checked for. And since there can only be one correct answer, 2016 must be divisible by 7…otherwise you’d have to say that C and E are both correct.

But even if you’re not willing to take that leap, you may still have the hunch that 7 is probably a factor of 2016, so you can start with choice D. Once you’ve divided 2016 by 9 (here you may have to go long division, or you can factor it out), you’re left with 224. And that’s not divisible by 3. Therefore, you know that 2016 cannot be divided evenly into sets of 54, so answer choice D must be correct. And more importantly, good number fluency should have allowed you to do that relatively quickly without the need for much (if any) long division.

So if you didn’t immediately think “divisible by 4 and 9!” when you saw the year 2016 pop up, make it your New Year’s resolution to start thinking that way. When you see numbers this year, start seeing them like a GMAT expert, taking note of clear factors and properties and being ready to quickly operate on that number.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

How to Choose the Right Number for a GMAT Variable Problem

Pi to the 36th digitWhen you begin studying for the GMAT, you will quickly discover that most of the strategies are, on the surface, fairly simple. It will not come as a terribly big surprise that selecting numbers and doing arithmetic is often an easier way of attacking a problem than attempting to perform complex algebra. There is, however, a big difference between understanding a strategy in the abstract and having honed that strategy to the point that it can be implemented effectively under pressure.

Now, you may be thinking, “How hard can it possibly be to pick numbers? I see an “x” and I decide x = 5. Not so complicated.” The art is in learning how to pick workable numbers for each question type. Different questions will require different types of numbers to create a scenario that truly is simpler than the algebra. The harder the problem, the more finesse that will be required when selecting numbers. Let’s start with a problem that doesn’t require much strategy:

If n=4p, where p is prime number greater than 2, how many different positive even divisors does n have, including n? 

(A) 2

(B) 3

(C) 4

(D) 6 

(E) 8 

Okay in this problem, “p” is a prime number greater than 2. So let’s say p = 3. If n = 4p, and 4p = 4*3 = 12. Let’s list out the factors of 12: 1, 2, 3, 4, 6, 12. The even factors here are 2, 4, 6, 12. There are 4 of them. So the answer is C. Not so bad, right? Just pick the first simple number that pops into your head and you’re off to the races. Bring on the test!

If only it were that simple for all questions. So let’s try a much harder question to illustrate the pitfalls of adhering to an approach that’s overly mechanistic:

The volume of water in a certain tank is x percent greater than it was one week ago. If r percent of the current volume of water in the tank is removed, the resulting volume will be 90 percent of the volume it was one week ago. What is the value of r in terms of x?

(A) x + 10

(B) 10x + 1

(C) 100(x + 10)

(D) 100 * (x+10)/(x+100)

(E) 100 * (10x + 1)/(10x+10)

You’ll notice quickly that if you simply declare that x = 10 and r =20, you may run into trouble. Say, for example, that the starting value from one week ago was 100 liters. If x = 10, a 10% increase will lead to a volume of 110 liters. If we remove 20% of that 110, we’ll be removing .20*110 = 22 liters, giving us 110-22 = 88 liters. But we’re also told that the resulting volume is 90% of the original volume! 88 is not 90% of 100, therefore our numbers aren’t valid. In instances like this, we need to pick some simple starting numbers and then calculate the numbers that will be required to fit the parameters of the question.

So again, say the volume one week ago was 100 liters. Let’s say that x = 20%, so the volume, after water is added, will be 100 + 20 = 120 liters.

We know that once water is removed, the resulting volume will be 90% of the original. If the original was 100, the volume, once water is removed, will be 100*.90 = 90 liters.

Now, rather than arbitrarily picking an “r”, we’ll calculate it based on the numbers we have. To summarize:

Start: 100 liters

After adding water: 120 liters

After removing water: 90 liters

We now need to calculate what percent of those 120 liters need to be removed to get down to 90. Using our trusty percent change formula [(Change/Original) * 100] we’ll get (30/120) * 100 = 25%.

Thus, when x = 20, r =25. Now all we have to do is substitute “x” with “20” in the answer choices until we hit our target of 25.

Remember that in these types of problems, we want to start at the bottom of the answer choice options and work our way up:

(E) 100 * (10x + 1)/(10x+10)

100 * (10*20 + 1)/(10*20+10) = 201/210. No need to simplify. There’s no way this equals 25.

(D) 100 * (x+10)/(x+100)

100 * (20+10)/(20+100) = 100 * (30/120) = 25. That’s it! We’re done. The correct answer is D.

Takeaways: Internalizing strategies is the first step in your process of preparing for the GMAT. Once you’ve learned these strategies, you need to practice them in a variety of contexts until you’ve fully absorbed how each strategy needs to be tweaked to fit the contours of the question. In some cases, you can pick a single random number. Other times, there will be multiple variables, so you’ll have to pick one or two numbers to start and then solve for the remaining numbers so that you don’t violate the conditions of the problem. Accept that you may have to make adjustments mid-stream. Your first selection may produce hairy arithmetic. There are no style point on the GMAT, so stay flexible, cultivate back-up plans, and remember that mental agility trumps rote memorization every time.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Quarter Wit, Quarter Wisdom: Calculating the Probability of Intersecting Events

Quarter Wit, Quarter WisdomWe know our basic probability formulas (for two events), which are very similar to the formulas for sets:

P(A or B) = P(A) + P(B) – P(A and B)

P(A) is the probability that event A will occur.

P(B) is the probability that event B will occur.

P(A or B) gives us the union; i.e. the probability that at least one of the two events will occur.

P(A and B) gives us the intersection; i.e. the probability that both events will occur.

Now, how do you find the value of P(A and B)? The value of P(A and B) depends on the relation between event A and event B. Let’s discuss three cases:

1) A and B are independent events

If A and B are independent events such as “the teacher will give math homework,” and “the temperature will exceed 30 degrees celsius,” the probability that both will occur is the product of their individual probabilities.

Say, P(A) = P(the teacher will give math homework) = 0.4

P(B) = P(the temperature will exceed 30 degrees celsius) = 0.3

P(A and B will occur) = 0.4 * 0.3 = 0.12

2) A and B are mutually exclusive events

If A and B are mutually exclusive events, this means they are events that cannot take place at the same time, such as “flipping a coin and getting heads” and “flipping a coin and getting tails.” You cannot get both heads and tails at the same time when you flip a coin. Similarly, “It will rain today” and “It will not rain today” are mutually exclusive events – only one of the two will happen.

In these cases, P(A and B will occur) = 0

3) A and B are related in some other way

Events A and B could be related but not in either of the two ways discussed above – “The stock market will rise by 100 points” and “Stock S will rise by 10 points” could be two related events, but are not independent or mutually exclusive. Here, the probability that both occur would need to be given to you. What we can find here is the range in which this probability must lie.

Maximum value of P(A and B):

The maximum value of P(A and B) is the lower of the two probabilities, P(A) and P(B).

Say P(A) = 0.4 and P(B) = 0.7

The maximum probability of intersection can be 0.4 because P(A) = 0.4. If probability of one event is 0.4, probability of both occurring can certainly not be more than 0.4.

Minimum value of P(A and B):

To find the minimum value of P(A and B), consider that any probability cannot exceed 1, so the maximum P(A or B) is 1.

Remember, P(A or B) = P(A) + P(B) – P(A and B)

1 = 0.4 + 0.7 – P(A and B)

P(A and B) = 0.1 (at least)

Therefore, the actual value of P(A and B) will lie somewhere between 0.1 and 0.4 (both inclusive).

Now let’s take a look at a GMAT question using these fundamentals:

There is a 10% chance that Tigers will not win at all during the whole season. There is a 20% chance that Federer will not play at all in the whole season. What is the greatest possible probability that the Tigers will win and Federer will play during the season?

(A) 55%

(B) 60%

(C) 70%

(D) 72%

(E) 80%

Let’s review what we are given.

P(Tigers will not win at all) = 0.1

P(Tigers will win) = 1 – 0.1 = 0.9

P(Federer will not play at all) = 0.2

P(Federer will play) = 1 – 0.2 = 0.8

Do we know the relation between the two events “Tigers will win” (A) and “Federer will play” (B)? No. They are not mutually exclusive and we do not know whether they are independent.

If they are independent, then the P(A and B) = 0.9 * 0.8 = 0.72

If the relation between the two events is unknown, then the maximum value of P(A and B) will be 0.8 because P(B), the lesser of the two given probabilities, is 0.8.

Since 0.8, or 80%, is the greater value, the greatest possibility that the Tigers will win and Federer will play during the season is 80%. Therefore, our answer is E.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTubeGoogle+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

4 Predictions for 2016: Trends to Look for in the Coming Year

Can you believe another year has already gone by? It seems like just yesterday that we were taking down 2014’s holiday decorations and trying to remember to write “2015” when writing down the date. Well, 2015 is now in the books, which means it’s time for us to stick our necks out and make a few predictions for what 2016 will bring in the world of college and graduate school testing and admissions. We don’t always nail all of our predictions, and sometimes we’re way off, but that’s what makes this predictions business kind of fun, right?

Let’s see how we do this year… Here are four things that we expect to see unfold at some point in 2016:

The College Board will announce at least one significant change to the New SAT after it is introduced in March.
Yes, we know that an all-new SAT is coming. And we also know that College Board CEO David Coleman is determined to make his mark and launch a new test that is much more closely aligned with the Common Core standards that Coleman himself helped develop before stepping into the CEO role at the College Board. (The changes also happen to make the New SAT much more similar to the ACT, but we digress.) The College Board’s excitement to introduce a radically redesigned test, though, may very well lead to some changes that need some tweaking after the first several times the new test is administered. We don’t know exactly what the changes will be, but the new test’s use of “Founding Documents” as a source of reading passages is one spot where we won’t be shocked to see tweaks later in 2016.

At least one major business school rankings publication will start to collect GRE scores from MBA programs.
While the GRE is still a long way from catching up to the GMAT as the most commonly submitted test score by MBA applicants, it is gaining ground. In fact, 29 of Bloomberg Businessweek‘s top 30 U.S. business schools now let applicants submit a score from either exam. Right now, no publication includes GRE score data in its ranking criteria, which creates a small but meaningful implication: if you’re not a strong standardized test taker, then submitting a GRE score may mean that an admissions committee will be more willing to take a chance and admit you (assuming the rest of your application is strong), since it won’t have to report your test score and risk lowering its average GMAT score.

Of course, when a school admits hundreds of applicants, the impact of your one single score is very small, but no admissions director wants to have to explain to his or her boss why the school admitted someone with a 640 GMAT score while all other schools’ average scores keep going up. Knowing this incentive is in place, it’s only a matter of time before Businessweek, U.S. News, or someone else starts collecting GRE scores from business schools for their rankings data.

An expansion of student loan forgiveness is coming.
It’s an election year, and not many issues have a bigger financial impact on young voters than student loan debt. The average Class of 2015 college grad was left school owing more than $35,000 in student loans, meaning that these young grads may have to work until the age of 75 until they can reasonably expect to retire. Already this year the government announced the Revised Pay As You Earn (REPAYE) Plan, which lets borrowers cap their monthly loan payments at 10% of their monthly discretionary income. One possible way the program could expand is by loosening the standards of the Public Service Loan Forgiveness (PSLF) Program. Right now a borrower needs to make on-time monthly payments for 10 straight years to be eligible; don’t be surprised if someone proposes shortening it to five or eight years.

The number of business schools using video responses in their applications will triple.
Several prominent business schools such as Kellogg, Yale SOM, and U. of Toronto’s Rotman School of Management (which pioneered the practice) have started using video “essays” in their application process. While the rollout hasn’t been perfectly smooth, and many applicants have told us that video responses make the process even more stressful, we think video is’t going away anytime soon. In fact, we think that closer to 10 schools will use video as part of the application process by this time next year.

If a super-elite MBA program such as Stanford GSB or Harvard Business School starts video responses, then you will probably see a full-blown stampede towards video. But, even without one of those names adopting it, we think the medium’s popularity will climb significantly in the coming year. It’s just such a time saver for admissions officers – one can glean a lot about someone with just a few minutes of video – that this trend will only accelerate in 2016.

Let’s check back in 12 months and see how we did. In the meantime, we wish you a happy, healthy, and successful 2016!

By Scott Shrum

GMAT Tip of the Week: Your GMAT New Year’s Resolution

GMAT Tip of the WeekHappy New Year! If you’re reading this on January 1, 2016, chances are you’ve made your New Year’s resolution to succeed on the GMAT and apply to business school. (Why else read a GMAT-themed blog on a holiday?) And if so, you’re in luck: anecdotally speaking, students who study for and take the GMAT in the first half of the year, well before any major admissions deadlines, tend to have an easier time grasping material and taking the test. They have the benefit of an open mind, the time to invest in the process, and the lack of pressure that comes from needing a massive score ASAP.

This all relates to how you should approach your New Year’s resolution to study for the GMAT. Take advantage of that luxury of time and lessened-pressure, and study the right way – patiently and thoroughly.

What does that mean? Let’s equate the GMAT to MBA admissions New Year’s resolution to the most common New Year’s resolution of all: weight loss.

Someone with a GMAT score in the 300s or 400s is not unlike someone with a weight in the 300s or 400s (in pounds). There are easy points to gain just like there are easy pounds to drop. For weight loss, that means sweating away water weight and/or crash-dieting and starving one’s self as long as one can. As boxers, wrestlers, and mixed-martial artists know quite well, it’s not that hard to drop even 10 pounds in a day or two…but those aren’t long-lasting pounds to drop.

The GMAT equivalent is sheer memorization score gain. Particularly if your starting point is way below average (which is around 540 these days), you can probably memorize your way to a 40-60 point gain by cramming as many rules and formulas as you can. And unlike weight loss, you won’t “give those points” back. But here’s what’s a lot more like weight loss: if you don’t change your eating/study habits, you’re not going to get near where you want to go with a crash diet or cram session. And ultimately those cram sessions can prove to be counterproductive over the long run.

The GMAT is a test not of surface knowledge, but of deep understanding and of application. And the the problem with a memorization-based approach is that it doesn’t include much understanding or application. So while there are plenty of questions in the below-average bucket that will ask you pretty directly about a rule or relationship, the problems that you’ll see as you attempt to get to above average and beyond will hinge more on your ability to deeply understand a concept or to apply a concept to a situation where you might not see that it even applies.

So be leery of the study plan that nets you 40-50 points in a few weeks (unless of course that 40 takes you from 660 to 700) but then holds you steady at that level because you’re only remembering and not *knowing* or *understanding*. When you’re studying in January for a test that you don’t need to take until the summer or fall, you have the luxury of starting patiently and building to a much higher score.

Your job this next month isn’t to memorize every rule under the sun; it’s to make sure you fundamentally understand the building blocks of arithmetic, algebra, logic, and grammar as it relates to meaning. Your score might not jump as high in January, but it’ll be higher when decision day comes later this fall.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

Quarter Wit, Quarter Wisdom: Basic Operations for GMAT Inequalities

Quarter Wit, Quarter WisdomWe know that we can perform all basic operations of addition, subtraction, multiplication and division on two equations:

a = b

c = d

When these numbers are equal, we know that:

a + c = b + d (Valid)

a – c = b – d (Valid)

a * c = b * d (Valid)

a / c = b / d (Valid assuming c and d are not 0)

When can we add, subtract, multiply or divide two inequalities? There are rules that we need to follow for those. Today let’s discuss those rules and the concepts behind them.

Addition:

We can add two inequalities when they have the same inequality sign.

a < b

c < d

a + c < b + d (Valid)

Conceptually, it makes sense, right? If a is less than b and c is less than d, then the sum of a and c will be less than the sum of b and d.

On the same lines:

a > b

c > d

a + c > b + d (Valid)

Case 2: What happens when the inequalities have opposite signs?

a > b

c < d

We need to multiply one inequality by -1 to get the two to have the same inequality sign.

-c > -d

Now we can add them.

a – c > b – d

Subtraction:

We can subtract two inequalities when they have opposite signs:

a > b

c < d

a – c > b – d (The result will take the sign of the first inequality)

Conceptually, think about it like this: from a greater number (a is greater than b), if we subtract a smaller number (c is smaller than d), the result (a – c) will be greater than the result obtained when we subtract the greater number from the smaller number (b – d).

Note that this result is the same as that obtained when we added the two inequalities after changing the sign (see Case 2 above). We cannot subtract inequalities if they have the same sign, so it is better to always stick to addition. If the inequalities have the same sign, we simply add them. If the inequalities have opposite signs, we multiply one of them by -1 (to get the same sign) and then add them (in effect, we subtract them).

Why can we not subtract two inequalities when they have the same inequality sign, such as when a > b and c > d?

Say, we have 3 > 1 and 5 > 1.

If we subtract these two, we get 3 – 5 > 1 – 1, or -2 > 0 which is not valid.

If instead it were 3 > 1 and 2 > 1, we would get 1 > 0 which is valid.

We don’t know how much greater one term is from the other and hence we cannot subtract inequalities when their inequality signs are the same.

Multiplication:

Here, the constraint is the same as that in addition (the inequality signs should be the same) with an extra constraint: both sides of both inequalities should be non-negative. If we do not know whether both sides are non-negative or not, we cannot multiply the inequalities.

If a, b, c and d are all non negative,

a < b

c < d

a*c < b*d (Valid)

When two greater numbers are multiplied together, the result will be greater.

Take some examples to see what happens in Case 1, or more numbers are negative:

-2 < -1

10 < 30

Multiply to get: -20 < -30 (Not valid)

-2 < 7

-8 < 1

Multiply to get: 16 < 7 (Not valid)

Division:

Here, the constraint is the same as that in subtraction (the inequality signs should be opposite) with an extra constraint: both sides of both inequalities should be non-negative (obviously, 0 should not be in the denominator). If we do not know whether both sides are positive or not, we cannot divide the inequalities.

a < b

c > d

a/c < b/d (given all a, b, c and d are positive)

The final inequality takes the sign of the numerator.

Think of it conceptually: a smaller number is divided by a greater number, so the result will be a smaller number.

Take some examples to see what happens in Case 1, or more numbers are negative.

1 < 2

10 > -30

Divide to get 1/10 < -2/30 (Not valid)

Takeaways: 

Addition: We can add two inequalities when they have the same inequality signs.

Subtraction: We can subtract two inequalities when they have opposite inequality signs.

Multiplication: We can multiply two inequalities when they have the same inequality signs and both sides of both inequalities are non-negative.

Division: We can divide two inequalities when they have opposite inequality signs and both sides of both inequalities are non-negative (0 should not be in the denominator).

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

How to Make Rate Questions Easy on the GMAT

Integrated Reasoning StrategiesI recently wrote about the reciprocal relationship between rate and time in “rate” questions. Occasionally, students will ask why it’s important to understand this particular rule, given that it’s possible to solve most questions without employing it.

There are two reasons: the first is that knowledge of this relationship can convert incredibly laborious arithmetic into a very straightforward calculation. And the second is that this same logic can be applied to other types of questions. The goal, when preparing for the GMAT, isn’t to internalize hundreds of strategies; it’s to absorb a handful that will prove helpful on a variety of questions.

The other night, I had a tutoring student present me with the following question:

It takes Carlos 9 minutes to drive from home to work at an average rate of 22 miles per hour.  How many minutes will it take Carlos to cycle from home to work along the same route at an average rate of 6 miles per hour?

(A) 26

(B) 33

(C) 36

(D) 44

(E) 48

This question doesn’t seem that hard, conceptually speaking, but here is how my student attempted to do it: first, he saw that the time to complete the trip was given in minutes and the rate of the trip was given in hours so he did a simple unit conversion, and determined that it took Carlos (9/60) hours to complete his trip.

He then computed the distance of the trip using the following equation: (9/60) hours * 22 miles/hour = (198/60) miles. He then set up a second equation: 6miles/hour * T = (198/60) miles. At this point, he gave up, not wanting to wrestle with the hairy arithmetic. I don’t blame him.

Watch how much easier it is if we remember our reciprocal relationship between rate and time. We have two scenarios here. In Scenario 1, the time is 9 minutes and the rate is 22 mph. In Scenario 2, the rate is 6 mph, and we want the time, which we’ll call ‘T.” The ratio of the rates of the two scenarios is 22/6. Well, if the times have a reciprocal relationship, we know the ratio of the times must be 6/22. So we know that 9/T = 6/22.

Cross-multiply to get 6T = 9*22.

Divide both sides by 6 to get T = 9*22/6.

We can rewrite this as T = (9*22)/(3*2) = 3*11 = 33, so the answer is B.

The other point I want to stress here is that there isn’t anything magical about rate questions. In any equation that takes the form a*b = c, a and b will have a reciprocal relationship, provided that we hold c constant. Take “quantity * unit price = total cost”, for example. We can see intuitively that if we double the price, we’ll cut the quantity of items we can afford in half. Again, this relationship can be exploited to save time.

Take the following data sufficiency question:

Pat bought 5 lbs. of apples. How many pounds of pears could Pat have bought for the same amount of money? 

(1) One pound of pears costs $0.50 more than one pound of apples. 

(2) One pound of pears costs 1 1/2 times as much as one pound of apples. 

Statement 1 can be tested by picking numbers. Say apples cost $1/pound. The total cost of 5 pounds of apples would be $5.  If one pound of pears cost $.50 more than one pound of apples, then one pound of pears would cost $1.50. The number of pounds of pears that could be purchased for $5 would be 5/1.5 = 10/3. So that’s one possibility.

Now say apples cost $2/pound. The total cost of 5 pounds of apples would be $10. If one pound of pears cost $.50 more than one pound of apples, then one pound of pears would cost $2.50. The number of pounds of pears that could be purchased for $10 would be 10/2.5 = 4. Because we get different results, this Statement alone is not sufficient to answer the question.

Statement 2 tells us that one pound of pears costs 1 ½ times (or 3/2 times) as much as one pound of apples. Remember that reciprocal relationship! If the ratio of the price per pound for pears and the price per pound for apples is 3/2, then the ratio of their respective quantities must be 2/3. If we could buy five pounds of apples for a given cost, then we must be able to buy (2/3) * 5 = (10/3) pounds of pears for that same cost. Because we can find a single unique value, Statement 2 alone is sufficient to answer the question, and we know our answer must be B.

Takeaway: Remember that in “rate” questions, time and rate will have a reciprocal relationship, and that in “total cost” questions, quantity and unit price will have a reciprocal relationship. Now the time you save on these problem-types can be allocated to other questions, creating a virtuous cycle in which your time management, your accuracy, and your confidence all improve in turn.

*GMATPrep questions courtesy of the Graduate Management Admissions Council.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Quarter Wit, Quarter Wisdom: Grammatical Structure of Conditional Sentences on the GMAT

Quarter Wit, Quarter WisdomToday, we will take a look at the various “if/then” constructions in the GMAT Verbal section. Let us start out with some basic ideas on conditional sentences (though I know that most of you will be comfortable with these):

A conditional sentence (an if/then sentence) has two clauses – the “if clause” (conditional clause) and the “then clause” (main clause).  The “if clause” is the dependent clause, meaning the verbs we use in the clauses will depend on whether we are talking about a real or a hypothetical situation.

Often, conditional sentences are classified into first conditional, second conditional and third conditional (depending on the tense and possibility of the actions), but sometimes we have a separate zero conditional for facts. We will follow this classification and discuss four types of conditionals:

1) Zero Conditional

These sentences express facts; i.e. implications – “if this happens, then that happens.”

  • If the suns shines, the clothes dry quickly.
  • If he eats bananas, he gets a headache.
  • If it rains heavily, the temperature drops.

These conditionals establish universally known facts or something that happens habitually (every time he eats bananas, he gets a headache).

2) First Conditional

These sentences refer to predictive conditional sentences. They often use the present tense in the “if clause” and future tense (usually with the word “will”) in the main clause.

  • If you come to  my place, I will help you with your homework.
  • If I am able to save $10,000 by year end, I will go to France next year.

3) Second Conditional

These sentences refer to hypothetical or unlikely situations in the present or future. Here, the “if clause” often uses the past tense and the main clause uses conditional mood (usually with the word “would”).

  • If I were you, I would take her to the dance.
  • If I knew her phone number, I would tell you.
  • If I won the lottery, I would travel the whole world.

4) Third Conditional

These sentences refer to hypothetical situations in the past – what could have been different in the past. Here, the “if clause” uses the past perfect tense and the main clause uses the conditional perfect tense (often with the words “would have”).

  • If you had told me about the party, I would have attended it.
  • If I had not lied to my mother, I would not have hurt her.

Sometimes, mixed conditionals are used here, where the second and third conditionals are combined. The “if clause” then uses the past perfect and the main clause uses  the word “would”.

  • If you had helped me then, I would be in a much better spot today.

Now that you know which conditionals to use in which situation, let’s take a look at a GMAT question:

Botanists have proven that if plants extended laterally beyond the scope of their root system, they will grow slower than do those that are more vertically contained.

(A) extended laterally beyond the scope of their root system, they will grow slower than do

(B) extended laterally beyond the scope of their root system, they will grow slower than

(C) extend laterally beyond the scope of their root system, they grow more slowly than

(D) extend laterally beyond the scope of their root system, they would have grown more slowly than do

(E) extend laterally beyond the scope of their root system, they will grow more slowly than do

Now that we understand our conditionals, we should be able to answer this question quickly. Scientists have established something here; i.e. it is a fact. So we will use the zero conditional here – if this happens, then that happens.

…if plants extend laterally beyond the scope of their root system, they grow more slowly than do…

So the correct answer must be (C).

A note on slower vs. more slowly – we need to use an adverb here because “slow” describes “grow,” which is a verb. So we must use “grow slowly”. If we want to show comparison, we use “more slowly”, so the use of “slower” is incorrect here.

Let’s look at another question now:

If Dr. Wade was right, any apparent connection of the eating of highly processed foods and excelling at sports is purely coincidental.

(A) If Dr. Wade was right, any apparent connection of the eating of

(B) Should Dr. Wade be right, any apparent connection of eating

(C) If Dr. Wade is right, any connection that is apparent between eating of

(D) If Dr. Wade is right, any apparent connection between eating

(E) Should Dr. Wade have been right, any connection apparent between eating

Notice the non-underlined part “… is purely coincidental” in the main clause. This makes us think of the zero conditional.

Let’s see if it makes sense:

If Dr. Wade is right, any connection … is purely coincidental.

This is correct. It talks about a fact.

Also, “eating highly processed foods and excelling at sports” is correct.

Hence, our answer must be (D).

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Listen to Yoda on Sentence Correction You Must

GMAT Tip of the WeekSpeak like Yoda this weekend, your friends will. As today marks the release of the newest Star Wars movie, Star Wars Episode VII: The Force Awakens, young professionals around the world are lining up dressed as their favorite robot, wookie, or Jedi knight, and greeting each other in Yoda’s famous inverted sentence structure. And for those who hope to awaken the force within themselves to conquer the evil empire that is the GMAT, Yoda can be your GMAT Jedi Master, too.

Learn from Yoda’s speech pattern, you must.

What can Yoda teach you about mastering GMAT Sentence Correction? Beware of inverted sentences, you should. Consider this example, which appeared on the official GMAT:

Out of America’s fascination with all things antique have grown a market for bygone styles of furniture and fixtures that are bringing back the chaise lounge, the overstuffed sofa, and the claw-footed bathtub.

(A) things antique have grown a market for bygone styles of furniture and fixtures that are bringing
(B) things antique has grown a market for bygone styles of furniture and fixtures that is bringing
(C) things that are antiques has grown a market for bygone styles of furniture and fixtures that bring
(D) antique things have grown a market for bygone styles of furniture and fixtures that are bringing
(E) antique things has grown a market for bygone styles of furniture and fixtures that bring

What makes this problem difficult is the inversion of the subject and verb. Much like Yoda’s habit of putting the subject after the predicate, this sentence flips the subject (“a market”) and the verb (“has grown”). And in doing so, the sentence gets people off track – many will see “America’s fascination” as the subject (and luckily so, since it’s still singular) or “all things antique” as the subject. But consider:

  • Antique things can’t grow. They’re old, inanimate objects (like those Luke Skywalker and Darth Vader action figures that your mom threw away that would now be worth a lot of money).
  • America’s fascination is the reason for whatever is growing. “Out of America’s fascination, America’s fascination is growing” doesn’t make any sense – the cause can’t be its own effect.

So, logically, “a market” has to be the subject. But in classic GMAT style, the testmakers hide the correct answer (B) behind a strange sentence structure. Two, really – people also tend to dislike “all things antique” (preferring “all antique things” instead), but again, that’s an allowable inversion in which the adjective goes after the noun.

Here is the takeaway: the GMAT will employ lots of strange sentence structures, including subject-verb inversion, a la Yoda (but only when it’s grammatically warranted), so you will often need to rely on “The Force” of logic to sift through complicated sentences. Here, that means thinking through logically what the subject of the sentence should be, and also removing modifiers like “out of America’s fascination…” to give yourself a more concise sentence on which to employ that logical thinking (the fascination is causing a market to develop, and that market is bringing back these old types of furniture).

Don’t let the GMAT Jedi mind-trick you out of the score you deserve. See complicated sentence structures, you will, so employ the force of logic, you must.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

How I Achieved GMAT Success Through Service to School and Veritas Prep

Service to School Bryan Young served in the United States Army as an enlisted infantryman for five years, with a fifteen month tour in Iraq from 06’-07’. After leaving the military in 2008, he completed a Bachelor’s Degree in Business Administration from the University of Washington. He started his career in the consumer packaged goods industry and is now looking to attend a top tier university to obtain an MBA. Along with help from Veritas Prep, he was able to raise his GMAT score from a 540 to a 690!

How did you hear about Veritas Prep?

I had been thinking about taking the GMAT for the last three years and knew that I would probably need the help of a prep course to be able to get a competitive score. Service to School, a non-profit that helps veterans make the transition from the military to undergraduate and graduate school, awarded me with a scholarship to Veritas Prep.

What was your initial Experience with the GMAT?

During my first diagnostic test, I was pretty overwhelmed. The questions were confusing and the length of the test was intimidating. Finishing the test with a 540 was a wakeup call for me. My goal was to score a 700 or higher and the score I achieved showed me just how much work I was going to need to put into the process.

How did the Veritas Prep Course help prepare you?

The resources that Veritas Prep provides are amazing. The books arrived within a few days and then I was ready to start taking the online classes. After a few classes I realized that I needed to brush up on some of the basics and was able to use their skill builders sections to get back on track. The online class format was great and helped me to learn the strategies and ask questions. Then the homework help line was where I was able to get answers on some of the more tricky questions I encountered.

Tell us about your test day experiences and how you felt throughout the experience?

The first two times I took the test I was still not as prepared as I need to be. The test day started well, but quickly went sour. I ran out of time on the integrated reasoning section and with my energy being low I wound up having my worst verbal performances.

One of the greatest aspects of Veritas Prep is that they allow you to retake the class if you feel like you need to take it again. The second time through the class helped me a lot more since I wasn’t struggling with not knowing some of the basics. This helped me to fully understand the strategies for the quant section and solidify my sentence corrections skills as well. One suggestion of eating a snickers bar (or some sugary snack) made a huge difference for my energy levels and concentration on test day.

After another month and a half of studying I took the GMAT again and was excited to see the 690 with an 8 on the integrated reasoning. The score was in the range I wanted and I couldn’t have been happier to be finished. Veritas Prep helped me so much throughout the year long process of beating the GMAT!

Need help preparing for the GMAT? Join us for one of our FREE online GMAT strategy sessions or sign up for one of our GMAT prep courses, which are starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

The Patterns to Solve GMAT Questions with Reversed-Digit Numbers

Essay The GMAT asks a fair number of questions about the properties of two-digit numbers whose tens and units digits have been reversed. Because these questions pop up so frequently, it’s worth spending a little time to gain a deeper understanding of the properties of such pairs of numbers. Like much of the content on the GMAT, we can gain understanding of these problems by simply selecting random examples of such numbers and analyzing and dissecting them algebraically.

Let’s do both.

First, we’ll list out some random pairs of two-digit numbers whose tens and units digits have been reversed: {34, 43}; {17, 71}; {18, 81.} Now we’ll see if we can recognize a pattern when we add or subtract these figures. First, let’s try addition: 34 + 43 = 77; 17 + 71 = 88; 18 + 81 = 99. Interesting. Each of these sums turns out to be a multiple of 11. This will be true for the sum of any two two-digit numbers whose tens and units digits are reversed. Next, we’ll try subtraction: 43 – 34 = 9; 71 – 17 = 54; 81 – 18 = 63; Again, there’s a pattern. The difference of each pair turns out to be a multiple of 9.

Algebraically, this is easy enough to demonstrate. Say we have a two-digit number with a tens digit of “a” and a units digit of “b”. The number can be depicted as 10a + b. (If that isn’t clear, use a concrete number to illustrate it to yourself. Let’s reuse “34”. In this case a = 3 and b = 4. 10a + b = 10*3 + 4 = 34. This makes sense. The number in the “tens” place should be multiplied by 10.) If the original number is 10a + b, then swapping the tens and units digits would give us 10b + a. The sum of the two terms would be (10a + b) + (10b + a) = 11a + 11b = 11(a + b.) Because “a” and “b” are integers, this sum must be a multiple of 11. The difference of the two terms would be  (10a + b) – (10b + a) = 9a – 9b = 9(a – b) and this number will be a multiple of 9.

Now watch how easy certain official GMAT questions become once we’ve internalized these properties:

The positive two-digit integers x and y have the same digits, but in reverse order. Which of the following must be a factor of x + y?

A) 6

B) 9

C) 10

D) 11

E) 14

If you followed the above discussion, you barely need to be conscious to answer this question correctly. We just proved that the sum of two-digit numbers whose units and tens digits have been reversed is 11! No need to do anything here. The answer is D. Pretty nice.

Let’s try another, slightly tougher one:

If a two-digit positive integer has its digits reversed, the resulting integer differs from the original by 27. By how much do the two digits differ?

A) 3

B) 4

C) 5

D) 6

E) 7

This one is a little more indicative of what we’re likely to encounter on the actual GMAT. It’s testing us on a concept we’re expected to know, but doing so in a way that precludes us from simply relying on rote memorization. So let’s try a couple of approaches.

First, we’ll try picking some numbers. Let’s use the answer choices to steer us. Say we try B – we’ll want two digits that differ by 4. So let’s use the numbers 84 and 48. Okay, we can see that the difference is 84 – 48 = 36. That difference is too big, it should be 27. So we know that the digits are closer together. This means that the answer must be less than 4. We’re done. The answer is A. (And if you were feeling paranoid that it couldn’t possibly be that simple, you could test two numbers whose digits were 3 apart, say, 14 and 41. 41-14 = 27. Proof!)

Alternatively, we can do this one algebraically. We know that if the original two-digit numbers were 10a +b, that the new number, whose digits are reversed, would be 10b + a. If the difference between the two numbers were 27, we’d derive the following equation: (10a + b) – (10b + a) = 27. Simplifying, we get 9a – 9b = 27. Thus, 9(a – b) = 27, and a – b = 3. Also not so bad.

Takeaway: Once you’ve completed a few hundred practice questions, you’ll begin to notice that a few GMAT strategies are applicable to a huge swath of different question types. You’re constantly picking numbers, testing answer choices, doing simple algebra, or applying a basic number property that you’ve internalized. In this case, the relevant number property to remember is that the sum of two two-digit numbers whose units and tens digits have been reversed is always a multiple of 11, and the difference of such numbers is always a multiple of 9. Generally speaking, if you encounter a particular question type more than once in the Official Guide, it’s always worth spending a little more time familiarizing yourself with it.

*Official Guide questions courtesy of the Graduate Management Admissions Council.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

How to Use Difference of Squares to Beat the GMAT

GMATIn Michael Lewis’ Flashboys, a book about the hazards of high-speed trading algorithms, Lewis relates an amusing anecdote about a candidate interviewing for a position at a hedge fund. During this interview, the candidate receives the following question: Is 3599 a prime number? Hopefully, your testing Spidey Senses are tingling and telling you that the answer to the question is going to incorporate some techniques that will come in handy on the GMAT. So let’s break this question down.

First, this is an interview question in which the interviewee is put on the spot, so whatever the solution entails, it can’t involve too much hairy arithmetic. Moreover, it is far easier to prove that a large number is NOT prime than to prove that it is prime, so we should be thinking about how we can demonstrate that this number possesses factors other than 1 and itself.

Whenever we’re given unpleasant numbers on the GMAT, it’s worthwhile to think about the characteristics of round numbers in the vicinity. In this case, 3599 is the same as 3600 – 1. 3600, the beautiful round number that it is, is a perfect square: 602. And 1 is also a perfect square: 12. Therefore 3600 – 1 can be written as the following difference of squares:

3600 – 1 = 602 – 12

We know that x– y= (x + y)(x – y), so if we were to designate “x” as “60” and “y” as “1”, we’ll arrive at the following:

60– 1= (60 + 1)(60 – 1) = 61 * 59

Now we know that 61 and 59 are both factors of 3599. Because 3599 has factors other than 1 and itself, we’ve proven that it is not prime, and earned ourselves a plumb job at a hedge fund. Not a bad day’s work.

But let’s not get ahead of ourselves. Let’s analyze some actual GMAT questions that incorporate this concept.

First:

999,9992 – 1 = 

A) 1010 – 2

B) (106 – 2) 2   

C) 105 (106 -2)

D) 106 (105 -2)

E) 106 (106 -2)

Notice the pattern. Anytime we have something raised to a power of 2 (or an even power) and we subtract 1, we have the difference of squares, because 1 is itself a perfect square. So we can rewrite the initial expression as 999,9992 – 12.

Using our equation for difference of squares, we get:

999,9992 – 12  = (999,999 +1)(999,999 – 1)

(999,999 + 1)(999,999 – 1) = 1,000,000* 999,998.

Take a quick glance back at the answer choices: they’re all in terms of base 10, so there’s a little work left for us to do. We know that 1,000,000 = 106  (Remember that the exponent for base 10 is determined by the number of 0’s in the figure.) And we know that 999,998 = 1,000,000 – 2 = 106 – 2, so 1,000,000* 999,998 = 106 (106 -2), and our answer is E.

Let’s try one more:

Which of the following is NOT a factor of 38 – 28?

A) 97

B) 65

C) 35

D) 13

E) 5

Okay, you’ll see quickly that 38 – 28 will involve same painful arithmetic. But thankfully, we’ve got the difference of two numbers, each of which has been raised to an even exponent, meaning that we have our trusty difference of squares! So we can rewrite 38 – 28 as (34)2 – (24)2. We know that 34 = 81 and 24 = 16, so (34)2 – (24)2 = 812 – 162. Now we’re in business.

812 – 162 = (81 + 16)(81 – 16) = 97 * 65.

Right off the bat, we can see that 97 and 65 are factors of our starting numbers, and because we’re looking for what is not a factor, A and B are immediately out. Now let’s take the prime factorization of 65. 65 = 13 * 5. So our full prime factorization is 97 * 13 * 5. Now we see that 13 and 5 are factors as well, thus eliminating D and E from contention. That leaves us with our answer C. Not so bad.

Takeaways:

  • The GMAT is not interested in your ability to do tedious arithmetic, so anytime you’re asked to find the difference of two large numbers, there is a decent chance that the number can be depicted as a difference of squares.
  • If you have the setup (Huge Number)2 – 1, you’re definitely looking at a difference of squares, because 1 is a perfect square.
  • If you’re given the difference of two numbers, both of which are raised to even exponents, this can also be depicted as a difference of squares, as all integers raised to even exponents are, by definition, perfect squares.

*Official Guide question courtesy of the Graduate Management Admissions Council.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And be sure to follow us on FacebookYouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Quarter Wit, Quarter Wisdom: Cyclicity in GMAT Remainder Questions (Part 2)

Quarter Wit, Quarter WisdomLast week, we reviewed the concepts of cyclicity and remainders and looked at some basic questions. Today, let’s jump right into some GMAT-relevant questions on these topics:

 

 

If n is a positive integer, what is the remainder when 3^(8n+3) + 2 is divided by 5?

(A) 0

(B) 1

(C) 2

(D) 3

(E) 4

In this problem, we are looking for the remainder when the divisor is 5. We know from last week that if we get the last digit of the dividend, we will be able to find the remainder, so let’s focus on finding the units digit of 3^(8n + 3) + 2.

The units digit of 3 in a positive integer power has a cyclicity of: 3, 9, 7, 1

So the units digit of 3^(8n + 3) = 3^(4*2n + 3) will have 2n full cycles of 3, 9, 7, 1 and then a new cycle will start:

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7

Since the exponent a remainder of 3, the new cycle ends at 3, 9, 7. Therefore, the units digit of 3^(8n + 3) is 7. When you add another 2 to this expression, the units digit becomes 7+2 = 9.

This means the units digit of 3^(8n+3) + 2 is 9. When we divide this by 5, the remainder will be 4, therefore, our answer is E.

Not so bad; let’s try a data sufficiency problem:

If k is a positive integer, what is the remainder when 2^k is divided by 10?

Statement 1: k is divisible by 10

Statement 2: k is divisible by 4

With this problem, we know that the remainder of a division by 10 can be easily obtained by getting the units digit of the number. Let’s try to find the units digit of 2^k.

The cyclicity of 2 is: 2, 4, 8, 6. Depending on the value of k is, the units digit of 2^k will change:

If k is a multiple of 4, it will end after one cycle and hence the units digit will be 6.

If k is 1 more than a multiple of 4, it will start a new cycle and the units digit of 2^k will be 2.

If k is 2 more than a multiple of 4, it will be second digit of a new cycle, and the units digit of 2^k will be 4.

If k is 3 more than a multiple of 4, it will be the third digit of a new cycle and the units digit of 2^k will be 8.

If k is 4 more than a multiple of 4, it will again be a multiple of 4 and will end a cycle. The units digit of 2^k will be 6 in this case.

and so on…

So what we really need to find out is whether k is a multiple of 4, one more than a multiple of 4, two more than a multiple of 4, or three more than a multiple of 4.

Statement 1: k is divisible by 10

With this statement, k could be 10 or 20 or 30 etc. In some cases, such as when k is 10 or 30, k will be two more than a multiple of 4. In other cases, such as when k is 20 or 40, k will be a multiple of 4. So for different values of k, the units digit will be different and hence the remainder on division by 10 will take multiple values. This statement alone is not sufficient.

Statement 2: k is divisible by 4

This statement tells you directly that k is divisible by 4. This means that the last digit of 2^k is 6, so when divided by 10, it will give a remainder of 6. This statement alone is sufficient. therefore our answer is B.

Now, to cap it all off, we will look at one final question. It is debatable whether it is within the scope of the GMAT but it is based on the same concepts and is a great exercise for intellectual purposes. You are free to ignore it if you are short on time or would not like to go an iota beyond the scope of the GMAT:

What is the remainder of (3^7^11) divided by 5?

(A) 0

(B) 1

(C) 2

(D) 3

(E) 4

For this problem, we need the remainder of a division by 5, so our first step is to get the units digit of 3^7^{11}. Now this is the tricky part – it is 3 to the power of 7, which itself is to the power of 11. Let’s simplify this a bit; we need to find the units digit of 3^a such that a = 7^{11}.

We know that 3 has a cyclicity of 3, 9, 7, 1. Therefore (similar to our last problem) to get the units digit of 3^a, we need to find whether a is a multiple of 4, one more than a multiple of 4, two more than a multiple of 4 or three more than a multiple of 4.

We need a to equal 7^{11}, so first we need to find the remainder when a is divided by 4; i.e. when 7^{11} is divided by 4.

For this, we need to use the binomial theorem we learned earlier in this post (or we can use the method of “pattern recognition”):

The remainder of 7^{11} divided by 4

= The remainder of (4 + 3)^{11} divided by 4

= The remainder of 3^{11} divided by 4

= The remainder of 3*3^{10} divided by 4

= The remainder of 3*9^5 divided by 4

= The remainder of 3*(8+1)^5 divided by 4

= The remainder of 3*1^5 divided by 4

= The remainder of 3 divided by 4, which itself = 3

So when 7^{11} is divided by 4, the remainder is 3. This means 7^{11} is 3 more than a multiple of 4; i.e. a is 3 more than a multiple of 4.

Now we go back to 3^a. We found that a is 3 more than a multiple of 4. So there will be full cycles (we don’t need to know the exact number of cycles) and then a new cycle with start with three digits remaining:

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7

With this pattern, we see the last digit of 3^7^11 is 7. When this 7 is divided by 5, remainder will be 2 – therefore, our answer is C.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

Quarter Wit, Quarter Wisdom: Cyclicity in GMAT Remainder Questions

Quarter Wit, Quarter WisdomUsually, cyclicity cannot help us when dealing with remainders, but in some cases it can. Today we will look at the cases in which it can, and we will see why it helps us in these cases.

First let’s look at a pattern:

 

20/10 gives us a remainder of 0 (as 20 is exactly divisible by 10)

21/10 gives a remainder of 1

22/10 gives a remainder of 2

23/10 gives a remainder of 3

24/10 gives a remainder of 4

25/10 gives a remainder of 5

and so on…

In the case of this pattern, 20 is the closest multiple of 10 that goes completely into all these numbers and you are left with the units digit as the remainder. Whenever you divide a number by 10, the units digit will be the remainder. Of course, if the units digit of a number is 0, the remainder will be 0 and that number will be divisible by 10 — but we already know that. So remainder when 467,639 is divided by 10 is 9. The remainder when 100,238 is divided by 10 is 8 and so on…

Along the same lines, we also know that every number that ends in 0 or 5 is a multiple of 5 and every multiple of 5 must end in either 0 or 5. So if the units digit of a number is 1, it gives a remainder of 1 when divided by 5. If the units digit of a number is 2, it gives a remainder of 2 when divided by 5. If the units digit of a number is 6, it gives a remainder of 1 when divided by 5 (as it is 1 more than the previous multiple of 5).

With this in mind:

20/5 gives a remainder of 0 (as 20 is exactly divisible by 5)

21/5 gives a remainder of 1

22/5 gives a remainder of 2

23/5 gives a remainder of 3

24/5 gives a remainder of 4

25/5 gives a remainder of 0 (as 25 is exactly divisible by 5)

26/5 gives a remainder of 1

27/5 gives a remainder of 2

28/5 gives a remainder of 3

29/5 gives a remainder of 4

30/5 gives a remainder of 0 (as 30 is exactly divisible by 5)

and so on…

So the units digit is all that matters when trying to get the remainder of a division by 5 or by 10.

Let’s take a few questions now:

What is the remainder when 86^(183) is divided by 10?

Here, we need to find the last digit of 86^(183) to get the remainder. Whenever the units digit is 6, it remains 6 no matter what the positive integer exponent is (previously discussed in this post).

So the units digit of 86^(183) will be 6. So when we divide this by 10, the remainder will also be 6.

Next question:

What is the remainder when 487^(191) is divided by 5?

Again, when considering division by 5, the units digit can help us.

The units digit of 487 is 7.

7 has a cyclicity of 7, 9, 3, 1.

Divide 191 by 4 to get a quotient of 47 and a remainder of 3. This means that we will have 47 full cycles of “7, 9, 3, 1” and then a new cycle will start and continue until the third term.

7, 9, 3, 1

7, 9, 3, 1

7, 9, 3, 1

7, 9, 3, 1

7, 9, 3

So the units digit of 487^(191) is 3, and the number would look something like ……………..3

As discussed, the number ……………..0 would be divisible by 5 and ……………..3 would be 3 more, so it will also give a remainder of 3 when divided by 5.

Therefore, the remainder of 487^(191) divided by 5 is 3.

Last question:

If x is a positive integer, what is the remainder when 488^(6x) is divided by 2?

Take a minute to review the question first. If you start by analyzing the expression 488^(6x), you will waste a lot of time. This is a trick question! The divisor is 2, and we know that every even number is divisible by 2, and every odd number gives a remainder 1 when divided by 2. Therefore, we just need to determine whether 488^(6x) is odd or even.

488^(6x) will be even no matter what x is (as long as it is a positive integer), because 488 is even and we know even*even*even……(any number of terms) = even.

So 488^(6x) is even and will give remainder 0 when it is divided by 2.

That is all for today. We will look at some GMAT remainders-cyclicity questions next week!

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: The Detroit Lions Teach How NOT to Take the GMAT

GMAT Tip of the WeekIf you’re applying to business schools in Round 2, you’re looking for good news (acceptance!) or a chance to advance to the next round (you’ve been invited to interview!) or even just a lack of bad news (you’re on the waitlist…there’s still a chance!) in January or February. Well if those who don’t learn from history are condemned to repeat it, you’d be well served to avoid the pitfalls of the Detroit Lions, an NFL franchise that hasn’t had January/February good news or a chance to advance since 1991.

Any Detroit native could write a Grishamesque (same thing year after year, but we keep coming back for more) series of books about the many losing-based lessons the Lions have taught over the years, but this particular season beautifully showcases one of the most important GMAT lessons of all:

Finish the job.

Six weeks ago, this lesson was learned as Calvin Johnson took the game-winning touchdown within inches of the goal line before having the ball popped out by Seattle Seahawks star Kam Chancellor. And last night this lesson was learned as Green Bay Packers star Aaron Rodgers completed a 60+ yard Hail Mary pass on an untimed final down.

On the GMAT, you have the same opportunities and challenges as the Detroit Lions do: stiff competition (there are Rodgerses and Chancellors hoping to get that spot at Harvard Business School, too) and a massive penalty for doing everything right until the last second. Lions fans and GMAT instructors share the same pain — our teams and our students are often guilty of doing absolutely everything right and then making one fatal mistake at the finish and not getting any credit for it. Consider the example:

A bowl of fruit contains 14 apples and 23 oranges. How many oranges must be removed so that 70% of the pieces of fruit in the bowl will be apples?

(A) 3

(B) 6

(C) 14

(D) 17

(E) 20

Here, most GMAT students get off to a great start, just like the Lions did going up 17-0. They know that the 14 apples (that number remains unchanged) need to represent 70% of the new total. If 14 = 0.7(x), then the algebra becomes quick. Multiply both sides by 10 to get rid of the decimal: 140 = 7x. Then divide both sides by 7 and you have x = 20. And you also have your first opportunity to “Lion up”: 20 is an answer choice! But 20 doesn’t represent the number of oranges; that’s the total for pieces of fruit after the orange removal. So 20 is a trap.

You then need to recognize that 14 of that 20 is apples, so you have 14 apples and 6 oranges in the updated bowl. But Lions beware! 6 is an answer choice, but it’s not the right one: you have 6 oranges LEFT but the question asks for the number REMOVED. That means that you have to subtract the 6 you kept from the 23 you started with, and the correct answer is D, 17.

What befalls many GMAT students is that ticking clock and the pressure to move on to the next problem. By succumbing to that time/pace pressure — or by being so relieved, and maybe even surprised, that their algebra is producing numbers that match the answer choices — they fail to play all the way to the final gun, and like the Lions, they tragically lose a “game” (or problem) that they should have won. Which, as any Lions fan will tell you, is tragic. When you get blown out in football or you simply can’t hack the math on the GMAT, it’s sad but not devastating: you’re just not good enough (sorry, Browns fans). But when you’ve proven that you’re good enough and lose out because you didn’t finish the job, that’s crushing.

Now, like Lions fans talking about the phantom facemask call last night, you may be thinking, “That’s unfair! What a dirty question to ask about how many ‘left over’ instead of how many remaining. I hate the GMAT and I hate the refs!” And regardless of whether you have a fair point, you have to recognize that it’s part of the game.

The GMAT won’t give you credit for being on the right track — you have to get the problem right and be ready for that misdirection in the question itself. So learn from the Lions and make sure you finish every problem by double-checking that you’ve answered exactly the question that they asked. Finish the job, and you won’t have to wait 24 years and counting to finally have good news in January.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

Is Your GMAT Score More Important Than Ever?

GMAT ReasoningThe dreaded GMAT has long been one of the most feared components of the MBA application process. For many years the importance of the GMAT has been a bit overvalued by applicants, with too much focus being placed on the score and not enough on other areas of the application process. Just as admissions committees’ consistent message of their reliance on holistic reviews of candidate profiles has begun to sink in, a shift has seemingly started back the other way.

Although there has been a consistent upward trends over the last few decades in GMAT scores across the board, over the last year or two in particular the average GMAT scores at top MBA programs like Northwestern’s Kellogg School, Chicago’s Booth School and Pennsylvania’s Wharton School have risen by record percentage points. These record averages should signal to prospective applicant’s the increased importance of the GMAT.

Now, GMAT scores have always been important aspects of the MBA admissions process, but should applicants be more concerned with the rising scores at these top MBA programs?  The quick answer is no!  But you do want to accept this answer with a bit of a caveat: with dramatically rising GMAT scores across the board, it is even more important for applicants to target programs that are a clear fit for their background and showcased aptitude (GPA/GMAT). More specifically, applying to programs where your GMAT score falls below the average score has become a riskier option.

The typical candidate should make sure they hit or are very close to the listed averages. Now for candidates coming from a more competitive applicant pool like the Indian male, White male, and Asian male, it is important to target a score above schools’ listed averages to ensure you stand out from the pack. For non-traditional applicants, a strong GMAT score can be a way to stand out in the face of rising scores and increased competition.

The main takeaway from this trend for all applicants should be to really focus up front on creating the right list of target schools. Mind you, this list should not simply be one of the top 10 programs. Instead, create a list where your academic aptitude, professional goals, and other data points all align with the programs you plan to apply to so that you are able to maximize your chances of gaining admission to your target schools.

Applying to business school? Call us at 1-800-925-7737 and speak with an MBA admissions expert today, or click here to take our free MBA Admissions Profile Evaluation for personalized advice for your unique application situation! As always, be sure to find us on Facebook, YouTube, Google+ and Twitter.

Dozie A. is a Veritas Prep Head Consultant for the Kellogg School of Management at Northwestern University. His specialties include consulting, marketing, and low GPA/GMAT applicants. You can read more of his articles here.

Quarter Wit, Quarter Wisdom: Cyclicity of Units Digits on the GMAT (Part 2)

Quarter Wit, Quarter WisdomAs discussed last week, all units digits have a cyclicity of 1 or 2 or 4. Digits 2, 3, 7 and 8 have a cyclicity of 4, i.e. the units digit repeats itself every 4 digit:

Cyclicity of 2: 2, 4, 8, 6

Cyclicity of 3: 3, 9, 7, 1

Cyclicity of 7: 7, 9, 3, 1

Cyclicity of 8: 8, 4, 2, 6

Digits 4 and 9 have a cyclicity of 2, i.e. the units digit repeats itself every 2 digits:

Cyclicity of 4: 4, 6

Cyclicity of 9: 9, 1

Digits 0, 1, 5 and 6 have a cyclicity of 1, i.e. the units digit is 0, 1, 5, or 6 respectively.

Now let’s take a look at how to apply these fundamentals:

What is the units digit of 813^(27)?

To get the desired units digit here, all we need to worry about is the units digit of the base, which is 3.

Remember, our cyclicity of 3 is 3, 9, 7, 1 (four numbers total).

We need the units digit of 3^(27). How many full cycles of 4 will be there in 27? There will be 6 full cycles because 27 divided by 4 gives 6 as quotient and 3 will be the remainder. So after 6 full cycles of 4 are complete, a new cycle will start:

3, 9, 7, 1

3, 9, 7, 1

… (6 full cycles)

3, 9, 7 (new cycle for remainder of 3)

7 will be the units digit of 3^(27), so 7 will be the units digit of 813^(27).

Let’s try another question:

What is the units digit of 24^(1098)?

To get the desired units digit here, all we need to worry about is the units digit of the base, which is 4.

Remember, our cyclicity of 4 is 4 and 6 (this time, only 2 numbers).

We need the units digit of 24^(1098) – every odd power of 24 will end in 4 and every even power of 24 will end in 6.

Since 1098 is even, the units digit of 24^(1098) is 6.

Not too bad; let’s try something a little harder:

What is the units digit of 75^(25)^5

Note here that you have 75 raised to power 25 which is further raised to the power of 5.

25^5 is not the same as 25*5 – it is 25*25*25*25*25 which is far more complicated. However, the simplifying element of this question is that the last digit of the base 75 is 5, so it doesn’t matter what the positive integer exponent is, the last digit of the expression will always be 5.

Now let’s take a look at a Data Sufficiency question:

Given that x and y are positive integers, what is the units digit of (5*x*y)^(289)?

Statement 1: x is odd.

Statement 2: y is even.

Here there is a new complication – we don’t know what the base is exactly because the base depends on the value of x and y. As such, the real question should be can we figure out the units digit of the base? That is all we need to find the units digit of this expression.

When 5 is multiplied by an even integer, the product ends in 0.

When 5 is multiplied by an odd integer, the product ends in 5.

These are the only two possible cases: The units digit must be either 0 or 5.

With Statement 1, we do not know whether y is odd or even, we only know that x is odd. If y is odd, x*y will be odd. If y is even, x*y will be even. Since we don’t know whether x*y is odd or even, we don’t know whether 5*x*y will end in 5 or 0, so this statement alone is not sufficient.

With Statement 2, if y is even, x*y will certainly be even because an even * any integer will equal an even integer. Therefore, it doesn’t matter whether x is odd or even – regardless, 5*x*y will be even, hence, it will certainly end in 0.

As we know from our patterns of cyclicity, 0 has a cyclicity of 1, i.e. no matter what the positive integer exponent, the units digit will be 0. Therefore, this statement alone is sufficient and the answer is B (Statement 2 alone is sufficient but Statement 1 alone is not sufficient).

Finally, let’s take a question from our own book:

If n and a are positive integers, what is the units digit of n^(4a+2) – n^(8a)?

Statement 1: n = 3

Statement 2: a is odd.

We know that the cyclicity of every digit is either 1, 2 or 4. So to know the units digit of n^{4a+2} – n^{8a}, we need to know the units digit of n. This will tell us what the cyclicity of n is and what the units digit of each expression will be individually.

Statement 1: n = 3

As we know from our patterns of cyclicity, the cyclicity of 3 is 3, 9, 7, 1

Plugging 3 into “n”, n^{4a+2} = 3^{4a+2}

In the exponent, 4a accounts for “a” full cycles of 4, and then a new cycle begins to account for 2.

3, 9, 7, 1

3, 9, 7, 1

3, 9

The units digit here will be 9.

Again, plugging 3 into “n”, n^{8a} = 3^{8a}

8a is a multiple of 4, so there will be full cycles of 4 only. This means the units digit of 3^{8a} will be 1.

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

3, 9, 7, 1

Plugging these answers back into our equation: n^{4a+2} – n^{8a} = 9 – 1

The units digit of the combined expression will be 9 – 1 = 8.

Therefore, this statement alone is sufficient.

In Statement 2, we are given what the exponents are but not what the value of n, the base, is. Therefore, this statement alone is not sufficient, and our answer is A (Statement 1 alone is sufficient but Statement 2 alone is not sufficient).

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: What Test-Takers Should Be Thankful For

GMAT Tip of the WeekIf you’re spending this Thanksgiving weekend studying for the GMAT in hopes of a monster score for your Round 2 applications, there’s a good chance you’re feeling anything but grateful. At the very least, that practice test kept you inside and away from the hectic horror that has become Black Friday, but it’s understandable that when you spend the weekend thinking more about pronouns than Pilgrims and modifiers than Mayflowers, your introduction to the holiday season has you saying “bah, humbug.”

As you study, though, keep the spirit of Thanksgiving close to your heart. Those who made the first pilgrimage to New England didn’t have it easy, either – Thanksgiving is about being grateful for the small blessings that allowed them to survive in the land of HBS, Yale, Sloan, and Tuck. And the GMAT gives you plenty to be thankful for as you attempt to replicate their journey to the heart of elite academia. This Thanksgiving, GMAT test-takers should be thankful for:

1) Answer Choices

While it’s normal to dislike standardized, multiple-choice tests, those multiple choices are often the key to solving problems efficiently and correctly. They let you know whether you can get away with an estimate, allow you to backsolve or pick numbers to test the choices, and offer you insight into how you should attack the problem (that square root of 3 probably came from a 30-60-90 triangle if you can find it). On the Verbal Section, they allow you to use process of elimination, and particularly on Sentence Correction, to see what the true Decision Points are. A test without answer choices would mean that you’d have to do every problem the long way, but those who know to be thankful for answer choices will often find a competitive advantage.

2) Right Triangles

Right triangles are everywhere on GMAT geometry problems, and learning to use them to your advantage gives you a huge (turkey?) leg up on the competition. Right triangles:

  • Provide you with side ratios, or at least the Pythagorean Theorem
  • Make the base-height combination for the area of a triangle easy (just use the two sides adjacent to the right angle as your base and height)
  • Allow you to use the Pythagorean Theorem to solve for the distance between any two points in the coordinate plane
  • Let you make the greatest difference between any two points in a square, rectangle, cylinder, or box the hypotenuse of a right triangle
  • Help you divide strange shapes into easy-to-solve triangles

Much of GMAT geometry comes down to finding and leveraging right triangles, so thankful that you have that opportunity.

3) Verbs

When there are too many differences between Sentence Correction answer choices, it can be difficult to determine which decision points are most important. One key: look for verbs. When answer choices have different forms of the same verb – whether different tenses or singular-vs.-plural – that’s nearly always a primary decision point and a decision that you can make well using logic. Does the timeline make sense or not? Is the subject singular or plural? Often the savviest test-takers are the ones who save the difficult decisions for last and look for verbs first. Whenever you see different versions of the same verb in the answer choices, be thankful – your job just got easier.

4) “The Other Statement”

Data Sufficiency is a challenging question type, and one that seems to always feature a very compelling trap answer. Very often that trap answer is tempting because:

A statement that didn’t look to be sufficient actually is sufficient.

A statement that looked sufficient actually isn’t.

And that, “Is this tricky statement sufficient or not?” decision is an incredibly difficult one in a vacuum, but the GMAT (thankfully!) gives you a clue: the other statement. When one statement is obvious, its role is often to serve as a clue (“you’d better consider whether you need to know this or not when you look at the other statement”) or a trap (“you actually don’t need this, but when we tempt you with it you’ll think you do”). In either case, the obvious statement is telling you what you need to consider – why would that piece of information matter, or not? So be thankful that Data Sufficiency doesn’t require you to confirm your decision on each statement alone before you get to look at them together; taking the hint from one statement is often the best way to effectively assess the other.

5) Extra Words in Critical Reasoning Conclusions

If you spend any of this holiday weekend watching football, watch what happens when the offense employs the “man in motion” play (having one of the wide receivers run from one side of the offense to the other). Either the defensive player opposite him follows (suggesting man coverage) or he doesn’t (suggesting zone). With the “man in motion”, the offense is probing the defense to see, “What kind of defense are you playing?”. On GMAT Critical Reasoning, extra words in the conclusion serve an almost identical purpose – if you’re looking carefully, you’ll see exactly what’s important to the problem:

Country X therefore has to increase jobs in oil refinement in order to avoid a surge in unemployment. (Why does it have to be refinement? The traps will be about other jobs related to oil but not specifically refinement.)

Therefore, Company Y needs to cut its marketing expenses. (Why marketing and not other kinds of expenses?)

The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods. (Solely? You can weaken this conclusion by finding just one alternate reason)

For much of the Verbal Section, the more words you have to read, the more difficult your job is to process them all. But on Critical Reasoning, be thankful when you see extra words in the conclusion – those words tell you exactly what game the author is playing.

6) The CAT Algorithm

For many test-takers, the computer-adaptive scoring algorithm is something to be angry or frustrated about, and certainly not something to be thankful for. But if you look from the right angle (and you know we’re already thankful for right angles…) there’s plenty to be happy about, including:

  • You’re allowed to miss questions and make mistakes. The CAT system ensures that everyone sees a challenging test, so everyone will make mistakes. You don’t have to be perfect (and probably shouldn’t try).
  • You get your scores immediately. Talk to your friends taking the LSAT and see how they feel about turning in their answer sheet and then…waiting. In an instant gratification society, the GMAT gives you that instant feedback you crave. Do well and celebrate; do worse than you thought and immediately start game-planning the next round while it’s fresh in your mind.
  • It favors the prepared. You’re reading a GMAT blog during your spare time… you’ll be among those who prepare! The pacing is tricky since you can’t return to problems later, but remember that everyone takes the same test. If you’ve prepared and have a good sense of how to pace yourself, you’ll do better than those who are surprised by the setup and don’t plan accordingly. An overall disadvantage can still be a terrific competitive advantage, so as you’re looking for GMAT-themed things to be thankful for, keep your preparation in mind and be thankful that you’re working harder than your competition and poised to see the rewards!

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

Quarter Wit Quarter Wisdom: Cyclicity of Units Digits on the GMAT

Quarter Wit, Quarter WisdomIn our algebra book, we have discussed finding and extrapolating patterns. In this post today, we will look at the patterns we get with various units digits.

The first thing you need to understand is that when we multiply two integers together, the last digit of the result depends only on the last digits of the two integers.

For example:

24 * 12 = 288

Note here: …4 * …2 = …8

So when we are looking at the units digit of the result of an integer raised to a certain exponent, all we need to worry about is the units digit of the integer.

Let’s look at the pattern when the units digit of a number is 2.

Units digit 2:

2^1 = 2

2^2 = 4

2^3 = 8

2^4 = 16

2^5 = 32

2^6 = 64

2^7 = 128

2^8 = 256

2^9 = 512

2^10 = 1024

Note the units digits. Do you see a pattern? 2, 4, 8, 6, 2, 4, 8, 6, 2, 4 … and so on

So what will 2^11 end with? The pattern tells us that two full cycles of 2-4-8-6 will take us to 2^8, and then a new cycle starts at 2^9. 

2-4-8-6

2-4-8-6

2-4

The next digit in the pattern will be 8, which will belong to 2^11. 

In fact, any integer that ends with 2 and is raised to the power 11 will end in 8 because the last digit will depend only on the last digit of the base. 

So 652^(11) will end in 8,1896782^(11) will end in 8, and so on…

A similar pattern exists for all units digits. Let’s find out what the pattern is for the rest of the 9 digits. 

Units digit 3:

3^1 = 3

3^2 = 9

3^3 = 27

3^4 = 81

3^5 = 243

3^6 = 729

The pattern here is 3, 9, 7, 1, 3, 9, 7, 1, and so on…

Units digit 4:

4^1 = 4

4^2 = 16

4^3 = 64

4^4 = 256

The pattern here is 4, 6, 4, 6, 4, 6, and so on… 

Integers ending in digits 0, 1, 5 or 6 have the same units digit (0, 1, 5 or 6 respectively), whatever the positive integer exponent. That is:

1545^23 = ……..5

1650^19 = ……..0

161^28 = ………1

Hope you get the point.

Units digit 7:

7^1 = 7

7^2 = 49

7^3 = 343

7^4 = ….1 (Just multiply the last digit of 343 i.e. 3 by another 7 and you get 21 and hence 1 as the units digit)

7^5 = ….7 (Now multiply 1 from above by 7 to get 7 as the units digit)

7^6 = ….9

The pattern here is 7, 9, 3, 1, 7, 9, 3, 1, and so on…

Units digit 8:

8^1 = 8

8^2 = 64

8^3 = …2

8^4 = …6

8^5 = …8

8^6 = …4

The pattern here is 8, 4, 2, 6, 8, 4, 2, 6, and so on…

Units digit 9: 

9^1 = 9

9^2 = 81

9^3 = 729

9^4 = …1

The pattern here is 9, 1, 9, 1, 9, 1, and so on…

Summing it all up:

1) Digits 2, 3, 7 and 8 have a cyclicity of 4; i.e. the units digit repeats itself every 4 digits.

Cyclicity of 2: 2, 4, 8, 6

Cyclicity of 3: 3, 9, 7, 1

Cyclicity of 7: 7, 9, 3, 1

Cyclicity of 8: 8, 4, 2, 6

2) Digits 4 and 9 have a cyclicity of 2; i.e. the units digit repeats itself every 2 digits.

Cyclicity of 4: 4, 6

Cyclicity of 9: 9, 1 

3) Digits 0, 1, 5 and 6 have a cyclicity of 1.

Cyclicity of 0: 0

Cyclicity of 1: 1

Cyclicity of 5: 5

Cyclicity of 6: 6

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

Is Technology Costing You Your GMAT Score?

Veritas Prep GMAT Prep Books on iPadI recently read Sherry Turkle’s Reclaiming Conversation: The Power of Talk in a Digital Age. While the book isn’t about testing advice, per se, its analysis of the costs of technology is so comprehensive that the insights are applicable to virtually every aspect of our lives.

The book’s core thesis – that our smartphones and tablets are fragmenting our concentration and robbing us of a fundamental part of what it means to be human – isn’t a terribly original one. The difference between Turkle’s work and less effective screeds about the evils of technology is the scope of the research she provides in demonstrating how the overuse of our devices is eroding the quality of our education, our personal relationships, and our mental health.

What’s amazing is that these costs are, to some extent, quantifiable. Ever wonder what the impact is of having most of our conversations mediated through screens rather than through hoary old things like facial expressions? College students in the age of smartphones score 40% lower on tests measuring indicators of empathy than college students from a generation ago. In polls, respondents who had access to smartphones by the time they were adolescents reported heightened anxiety about the prospect of face-to-face conversations in general.

Okay, you say. Disturbing as that is, those findings have to do with interpersonal relationships, not education. Can’t technology be used to enhance the learning environment as well? Though it would be silly to condemn any technology as wholly corrosive, particularly in light of the fact that most schools are making a concerted effort to incorporate laptops and tablets in the classroom, Turkle makes a persuasive case that the overall costs outweigh the benefits.

In one study conducted by Pam Mueller and Daniel Oppenheimer, the researchers compared the retention rates of students who took notes on their laptops versus those who took notes by hand. The researchers’ assumption had always been that taking notes on a laptop would be more beneficial, as most of us can type faster than we can write longhand. Much to their surprise, the students who took notes by hand did significantly better than those who took notes on their laptops when tested on the contents of a lecture a week later.

The reason, Mueller and Oppenheimer speculate, is that because the students writing longhand couldn’t transcribe fast enough to record everything, they had to work harder to filter the information they were provided, and this additional cognitive effort allowed them to retain more. The ease of transcription – what we perceive as a benefit of technology – actually proved to be a cost. Even more disturbing, another study indicated that the mere presence of a smartphone – even if the phone is off – will cause everyone in its presence to retain less of a lecture, not just the phone’s owner.

I’ve been teaching long enough that when I first started, it was basically unheard of for a student’s attention to wander because he’d been distracted by a device. Smartphones didn’t exist yet. No one brought laptops to class. Now, if I were to take a poll, I’d be surprised if there were a single student in class who didn’t at least glance at a smartphone during the course of a lesson. One imagines that the same is true when students are studying on their own – a phone is nearby, just in case something important comes up. I’d always assumed the presence of these devices was relatively harmless, but if a phone that’s off can degrade the quality of our study sessions, just imagine the impact of a phone that continually pings and buzzes as fresh texts, emails and notifications come in.

The GMAT is a four-hour test that requires intense focus and concentration, so anything that hampers our ability to focus is a potential drag on our scores. There’s no easy solution here. I’m certainly not advocating that anyone throw away their smartphone – the fact that certain technology has costs associated with it is hardly a reason to discard that technology altogether. There are plenty of well-documented educational benefits: one can use a long train ride as an opportunity to do practice problems or watch a lecture. We can easily store data that can shed light on where we need to focus our attention in future study sessions. So the answer isn’t a draconian one in which we have to dramatically alter our lifestyles. Technology isn’t going anywhere – it’s a question of moderation.

Takeaways: No rant about the costs of technology is going to be terribly helpful without an action plan, so here’s what I suggest:

  • Put the devices away in class and take notes longhand. Whether you’re in a GMAT prep class, or an accounting class in your MBA program, this will benefit both you and your classmates.
  • If you aren’t using your device to study, turn it off, and make sure it’s out of sight when you work. The mere visual presence of a smartphone will cause you to retain less.
  • Give yourself at least 2 hours of device-free time each day. This need not be when you’re studying. It can also be when you’re out to dinner with friends or spending time with family. In addition to improving your interpersonal relationships, conversation actually makes you smarter.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And, be sure to follow us on Facebook, YouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

What to Do if You’re Struggling with GMAT Solutions

stressed-studentOne of the most misleading parts of the whole GMAT experience is the process of reading the solution to a math problem in the Quant section. When you try the problem, you struggle, sweat, and go nowhere; when they explain the problem, they wave a snooty, know-it-all magic wand that clears everything up. But how did they think of that? What can you do to think like them (or barring that, where do they keep that magic wand, and how late do we have to break into their house to be sure they’re asleep when we steal it)?

The short answer is that they struggled just like you did, but like anybody else, they wanted to make it look easy. (Think of all the time some people spend preening their LinkedIn or their Instagram: you only ever see the flashy corporate name and the glamour shot, never the 5 AM wake up call or the 6 AM look in the mirror.) Solution writers, particularly those who work for the GMAC, never seem to tell you that problem solving is mostly about blundering through a lot of guesswork before hitting upon a pattern, but that’s really what it is. Your willingness to blunder around until you hit something promising is a huge part of what’s being tested on the GMAT; after all, as depressing as it sounds, that’s basically how life works.

Here’s a great example:

I haven’t laid eyes on it in thirty years, but I still remember that the rope ladder to my childhood treehouse had exactly ten rungs. I was a lot shorter then, and a born lummox, so I could only climb the ladder one or two rungs at a time. I also had more than a touch of childhood OCD, so I had to climb the ladder a different way every time. After how many trips up did my OCD prevent me from ever climbing it again? (In other words, how many different ways was I able to climb the ladder?)

A) 55       

B) 63       

C) 72       

D) 81        

E) 89

Just the thought of trying 55 to 89 different permutations of climbing the ladder has my OCD going off like a car alarm, so I’m going to look for an easier way of doing this. It’s a GMAT problem, albeit one on the level of a Google interview question, so it must have a simple solution. There has to be a pattern here, or the problem wouldn’t be tested. Maybe I could find that pattern, or at least get an idea of how the process works, if I tried some shorter ladders.

Suppose the ladder had one rung. That’d be easy: there’s only one way to climb it.

Now suppose the ladder had two rungs. OK, two ways: I could go 0-1 then 1-2, or straight from 0-2 in a single two step, so there are two ways to climb the ladder.

Now suppose that ladder had three rungs. 0-1, 1-2, 2-3 is one way; 0-2, 2-3 is another; 0-1, 1-3 is the third. So the pattern is looking like 1, 2, 3 … ? That can’t be right! Doubt is gnawing at me, but I’m going to give it one last shot.

Suppose that the ladder had four rungs. I could do [0-1-2-3-4] or [0-1-3-4] or [0-1-2-4] or [0-2-4] or [0-2-3-4]. So there are five ways to climb it … wait, that’s it!

While I was mucking through the ways to climb my four-rung ladder, I hit upon something. When I take my first step onto the ladder, I either climb one rung or two. If I climb one rung, then there are 3 rungs left: in other words, I have a 3-rung ladder, which I can climb in 3 ways, as I saw earlier. If my step is a two-rung step instead, then there are 2 rungs left: in other words, a 2-rung ladder, which I can climb in 2 ways. Making sense?

By the same logic, if I want to climb a 5-rung ladder, I can start with one rung, then have a 4-rung ladder to go, or start with two rungs, then have a 3-rung ladder to go. So the number of ways to climb a 5-rung ladder = (the number of ways to climb a 3-rung ladder) + (the number of ways to climb a 4-rung ladder). Aha!

My pattern starts 1, 2, 3, so from there I can find the number of ways to climb each ladder by summing the previous two. This gives me a 1-, 2-, 3-, … rung ladder list of 1, 2, 3, 5, 8, 13, 21, 34, 55, and 89, so a 10-rung ladder would have 89 possible climbing permutations, and we’re done.

And the lesson? Much like a kid on a rope ladder, for a GMAT examinee on an abstract problem there’s often no “one way” to do the problem, at least not one that you can readily identify from the first instant you start. Very often you have to take a few small steps so that in doing so, you learn what the problem is all about. When all else fails in a “big-number” problem, try testing the relationship with small numbers so that you can either find a pattern or learn more about how you can better attack the bigger numbers. Sometimes your biggest test-day blunder is not allowing yourself to blunder around enough to figure the problem out.

Congratulations: that’s the hardest GMAT problem you’ve solved yet! (And bonus points if you noticed that the answer choices differed by 8, 9, 9, and 8. I still have OCD, and a terrible sense of humor.)

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

You Can Do It! How to Work on GMAT Work Problems

Pump UpRate questions, so far as I can remember, have been a staple of almost every standardized test I’ve ever taken. I recall seeing them on proficiency tests in grade school. They showed up on the SAT. They were on the GRE. And, rest assured, dear reader, you will see them on the GMAT. What’s peculiar is that despite the apparent ubiquity of these problems, I never really learned how to do them in school. This is true for many of my students as well, as they come into my class thinking that they’re just not very good at these kinds of questions, when, in actuality, they’ve just never developed a proper approach. This is doubly true of work problems, which are just a kind of rate problem.

When dealing with a complex work question there are typically only two things we need to keep in mind, aside from our standard “rate * time = work” equation. First, we know that rates are  additive. If I can do 1 job in 4 hours, my rate is 1/4. If you can do 1 job in 3 hours, your rate is 1/3. Therefore, our combined rate is 1/4 + 1/3, or 7/12. So we can do 7 jobs in 12 hours.

The second thing we need to bear in mind is that rate and time have a reciprocal relationship. If our rate is 7/12, then the time it would take us to complete a job is 12/7 hours. Not so complex. What’s interesting is that these simple ideas can unlock seemingly complex questions. Take this official question, for example:

Pumps A, B, and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 6/5 hours; pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A, B, and C, operating simultaneously, to fill the tank.

A) 1/3

B) 1/2

C) 2/3

D) 5/6

E) 1

So let’s start by assigning some variables. We’ll call the rate for p ump A, Ra. Similarly, we’ll designate the rate for pump B as Rb,and the rate for pump C as Rc.

If the time for A and B together to fill the tank is 6/5 hours, then we know that their combined rate is 5/6, because again, time and rate have a reciprocal relationship. So this first piece of information yields the following equation:

Ra + Rb = 5/6.

If A and C can fill the tank in 3/2 hours, then, employing identical logic, their combined rate will be 2/3, and we’ll get:

Ra + Rc = 2/3.

Last, if B and C can fill tank in 2 hours, then their combined rate will be ½, and we’ll have:

Rb+ Rc = 1/2.

Ultimately, what we want here is the time it would take all three pumps working together to fill the tank. If we can find the combined rate, or Ra + Rb + Rc, then all we need to do is take the reciprocal of that number, and we’ll have our time to full the pump. So now, looking at the above equations, how can we get Ra + Rb + Rc on one side of an equation? First, let’s line our equations up vertically:

 Ra + Rb = 5/6.

Ra + Rc = 2/3.

Rb+ Rc = 1/2.

 Now, if we sum those equations, we’ll get the following:

2Ra + 2Rb + 2Rc = 5/6 + 2/3 + 1/2. This simplifies to:

2Ra + 2Rb + 2Rc = 5/6 + 4/6 + 3/6 = 12/6 or 2Ra + 2Rb + 2Rc  = 2.

Dividing both sides by 2, we’ll get: Ra + Rb + Rc  = 1.

This tells us that the pumps, all working together can do one tank in one hour. Well, if the rate is 1, and the time is the reciprocal of the rate, it’s pretty obvious that the time to complete the task is also 1. The answer, therefore, is E.

Takeaway: the most persistent myth we have about our academic limitations is that we’re simply not good at a certain subset of problems when, in truth, we just never properly learned how to do this type of question. Like every other topic on the GMAT, rate/work questions can be mastered rapidly with a sound framework and a little practice. So file away the notion that rates can be added in work questions and that time and rate have a reciprocal relationship. Then do a few practice questions, move on to the next topic, and know that you’re one step closer to mastering the skills that will lead you to your desired GMAT score.

*GMATPrep question courtesy of the Graduate Management Admissions Council.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And, be sure to find us on Facebook, YouTubeGoogle+ and Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Don’t Panic on the GMAT!

Letter of RecommendationYou’ve made it. After months of study, mountains of flash cards, and enough time spent on our YouTube channel that you’re starting to feel like Brian Galvin is one of your roommates, you’re at the test center and the GMAT — not the essay or something, but the real GMAT, in all its evil glory, complete with exponents and fractions — is about to begin. You’re nervous but excited, and cautiously optimistic for the first question: maybe it’ll be something like “What’s (2²)³?” or a work rate problem about how long it’d take George Jetson to burn down a widget factory. You mostly remember these questions, so you click “Begin”, and this is what you see:

A palindrome is a number that reads the same front-to-back as it does back-to-front (e.g. 202, 575, 1991, etc.) p is the smallest integer greater than 200 that is both a prime and a palindrome. What is the sum of the digits of p?

A) 3

B) 4

C) 5

D) 6

E) 7

Thud.

I don’t know about you, but I’m petrified. I mean, yeah, I know what you’re saying — I’m the bozo who just dreamed up that question — but I don’t know where it came from, and I’m sort of thinking I might need to summon an exorcist, because I must be possessed by a math demon. What does that question even say? How the heck are we going to solve it?

This is such a common GMAT predicament to be in that I’m willing to bet that 99% of test takers experience it: the feeling that you don’t even know what the question is saying, and the sense of creeping terror that maybe you don’t know what any of these questions are saying. This is by design, of course. The test writers love these sort of “gut check” questions that test your ability to calmly unpack and reason out a cruel and unusual prompt. So many students take themselves out of the game by panicking, but like any GMAT question, once we get past the intimidation factor, the problem is simple at heart. Let’s try to model the process.

We’ll start by clarifying our terms. Palindrome, palindrome … what on earth is a palindrome!? Is that some sort of hovercraft where Sarah Palin lives? Where are our flash cards? Maybe we should just go to law school or open a food truck or something, this test is absurd.

Wait, the answer is right in front of us, in the very first line! “A palindrome is a number that reads the same back-to-front as it does front-to-back.” Phew, OK, and there are even some examples. So a palindrome is a number like 101, 111, 121, etc. Alright, got that. And it’s prime … prime, prime … OK, right, that WAS on a flashcard: a prime number is a number with exactly two factors, such as 2, or 3, or 5, or 7. So if we were to make lists of each of these numbers, primes and palindromes, we’d have

Primes: 2, 3, 5, 7, 11, 13, 17, 19, …

Palindromes: 101, 111, 121, 131, …

and we want the first number that’s greater than 200 that appears on both lists. OK!

Now let’s think of where to start. We know our number is greater than 200, so 202 seems promising. But that can’t be prime: it’s even, so it has at least three factors (1, itself, and 2). Great! We can skip everything that begins/ends with 2, and fast forward to 303. That looks prime, but what was it that Brian kept telling us about divisibility by 3 … ah, yes, test the sum of the digits! 3 + 0 + 3 = 6, and 6 divides by 3, so 303 also divides by 3.

Our next candidate is 313. This seems to be our final hurdle: a lot of quick arithmetic. That’s what the question is testing, after all, right? How quickly can you factor 313?

It sure seems that way, but take one last look at the answers. The GMAT tests efficiency as much as anything else, and it has a way of hiding easter eggs for the observant. Our largest answer is 7, and what’s 3+1+3? 7! So this MUST be the answer, and any time spent factoring 313 is wasted time.

We made it! In hindsight, that didn’t really feel like a math problem, did it? It was testing our ability to:

1) Remember a definition (“prime”)

2) Actually read the question stem (“a palindrome is…”)

3) Not panic, and try a few numbers (“202”? “303”?)

4) Realize that heavy calculation is for suckers, and that the answer might be right in front of us (“check the answers”)

So we just had to remember, actually read the directions, have the courage to try something to see where it leads, and look for clues directly around us. I don’t know about you, but if I were running a business, those are exactly the sort of skills I’d want my employees to have; maybe these test writers are on to something after all!

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube, Google+, and Twitter!

Quarter Wit, Quarter Wisdom: Permutation Involving Sum of Digits

Quarter Wit, Quarter WisdomWe have seen in previous posts how to deal with permutation and combination questions on the GMAT. There is a certain variety of questions that involve getting a bunch of numbers using permutation, and then doing some operations on the numbers we get. The questions can get a little overwhelming considering the sheer magnitude of the number of numbers involved! Let’s take a look at that concept today. We will explain it using an example and then take a question as an exercise:

 

What is the sum of all four digit integers formed using the digits 1, 2, 3 and 4 such that each digit is used exactly once in each integer?

First of all, we will use our basic counting principle to find the number of integers that are possible.

The first digit can be chosen in 4 ways. The next one in 3 ways since each digit can be used only once. The next one in 2 ways and there will be only one digit left for the last place.

This gives us a total of 4*3*2*1 = 24 ways of writing such a four digit number. This is what some of the numbers will look like:

1234

1243

1324

1342

2143

4321

Now we need to add these 24 integers to get their sum. Note that since each digit has an equal probability of occupying every place, out of the 24 integers, six integers will have 1 in the units place, six will have 2 in the units place, another six will have 3 in the units place and the rest of the six will have 4 in the units place. The same is true for all places – tens, hundreds and thousands.

Imagine every number written in expanded form such as:

1234 = 1000 + 200 + 30 + 4

2134 = 2000 + 100 + 30 + 4

…etc.

For the 24 numbers, we will get six 1000’s, six 2000’s, six 3000’s and six 4000’s.

In addition, we will get six 100’s, six 200’s, six 300’s and six 400’s.

For the tens place, will get six 10’s, six 20’s, six 30’s and six 40’s.

And finally, in the ones place we will get six 1’s, six 2’s, six 3’s and six 4’s.

Therefore, the total sum will be:

6*1000 + 6*2000 + 6*3000 + 6*4000 + 6*100 + 6*200 + … + 6*3 + 6*4

= 6*1000*(1 + 2 + 3 + 4) + 6*100*(1 + 2 + 3 + 4) + 6*10*(1 + 2 + 3 + 4) + 6*1*(1 + 2 + 3 + 4)

= 6*1000*10 + 6*100*10 + 6*10*10 + 6*10

= 6*10*(1000 + 100 + 10 + 1)

= 1111*6*10

= 66660

Note that finally, there aren’t too many actual calculations, but there is some manipulation involved. Let’s look at a GMAT question using this concept now:

What is the sum of all four digit integers formed using the digits 1, 2, 3 and 4 (repetition is allowed)

A444440

B) 610000

C) 666640

D) 711040

E) 880000

Conceptually, this problem isn’t much different from the previous one.

Using the same basic counting principle to get the number of integers possible, the first digit can be chosen in 4 ways, the next one in 4 ways, the next one in again 4 ways and finally the last digit in 4 ways. This is what some of the numbers will look like:

1111

1112

1121

and so on till 4444.

As such, we will get a total of 4*4*4*4 = 256 different integers.

Now we need to add these 256 integers to get their sum. Since each digit has an equal probability of occupying every place, out of the 256 integers, 64 integers will have 1 in the units place, 64 will have 2 in the units place, another 64 integers will have 3 in the units place and the rest of the 64 integers will have 4 in the units place. The same is true for all places – tens, hundreds and thousands.

Therefore, the total sum will be:

64*1000 + 64*2000 + 64*3000 + 64*4000 + 64*100 + 64*200 + … + 64*3 + 64*4

= 1000*(64*1 + 64*2 + 64*3 + 64*4) + 100*(64*1 + 64*2 + 64*3 + 64*4) + 10*(64*1 + 64*2 + 64*3 + 64*4) + 1*(64*1 + 64*2 + 64*3 + 64*4)

= (64*1 + 64*2 + 64*3 + 64*4) * (1000 + 100 + 10 + 1)

= 64*10*1111

= 711040

So our answer is D.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube and Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

Use Number Lines on the GMAT, Not Memory!

SAT/ACTI’ve written in the past about how the biggest challenge on many GMAT questions is the strain they put on our working memory. Working memory, or our ability to process information that we hold temporarily, is by definition quite limited. It’s why phone numbers only contain seven digits – any more than that and most people wouldn’t be able to recall them. (Yes, there was a time, in the dark and distant past, when we had to remember phone numbers.)

One of the most simple and effective strategies we can deploy to combat our working memory limitations is to simply list out the sample space of scenarios we’re dealing with. If we were told, for example, that x is a prime number less than 20, rather than internalize this information, we can jot down x = 2, 3, 5, 7, 11, 13, 17, or 19. The harder and more abstract the question, the more necessary such a strategy will prove to be.

Take this challenging Data Sufficiency question, for example:

On the number line, the distance between x and y is greater than the distance between x and z. Does z lie between x and y on the number line?

1) xyz < 0

2) xy <0

The reader is hereby challenged to attempt this exercise in his or her head without inducing some kind of hemorrhage.

So, rather than try to conceptualize this problem mentally, let’s start by actually writing down all the number line configurations that we might have to deal with before even glancing at the statements. We know that x and z are closer than x and y. So we could get the following:

x____z_______________________y

z____x_______________________y

Or we can swap x and y to generate a kind of mirror image

y______________________x_____z

y______________________z_____x

The above number lines are the only four possibilities given the constraints provided in the question stem. Now we have something concrete and visual that we can use when evaluating the statements.

Statement 1 tells us that the product of the three variables is negative. If you’ve internalized your number properties – and we heartily encourage that you do – you know that a product is negative if there are an odd number of negative elements in said product. In this case, that means that either one of the variables is negative, or all three of them are. So let’s use say one of the variables is negative. By placing a 0 strategically, we can use any of our above number lines:

x__0__z______________________y

z__0__x______________________y

y__0___________________x_____z

y__0___________________z_____x

Each of these scenarios will satisfy that first statement. But we only need two.

In our first number line, z is between x and y, so we get a YES to the question.

In our second number line, z is not between x and y, so we get a NO to the question.

Because we can get a YES or a NO to the original question, Statement 1 alone is not sufficient. Eliminate answer choices A and D.

Statement 2 tells us that the product of x and y is negative. Thus, we know that one of the variables is positive, and one of the variables is negative. Again, we can simply peruse our number lines and select a couple of examples that satisfy this condition.

In our first number line, z is between x and y, so we get a YES to the question.

In our third number line, z is not between x and y, so we get a NO to the question.

Like with Statement 1, because we can get a YES or NO to the original question, Statement 2 alone is also not sufficient. Eliminate answer choice B.

When testing the statements together, we know two pieces of information. Statement 1 tells us that either one variable is negative or all three are. Statement 2 tells us that, between x and y, we have one negative and one positive. Therefore, together, we know that either x or y is negative, and the remaining variables are all positive. Now all we have to do is peruse our sample space and locate these scenarios. It turns out that we can use the same two number lines we used when testing Statement 2:

In our first number line, z is between x and y, so we get a YES to the question.

In our third number line, z is not between x and y, so we get a NO to the question.

So even together, the statements are not sufficient to answer the question – the correct answer is E.

Takeaway: on the GMAT there’s no reason to strain your brain any more than is necessary. The more concrete you can make the information you’re provided on a given question, the more likely it is that you’ll be able to properly execute whatever math or logic maneuvers you’re asked to perform.

*GMATPrep question courtesy of the Graduate Management Admissions Council.

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By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.

Burn the Which! On the GMAT, That Is…

holy-grail-witchIt’s Halloween as I write this, but by the time you read it, November will be upon us, and you’ll be several days into a serious candy hangover. With that in mind, you’re probably in the mood for something boring and self-disciplined — or just to throw up — and I couldn’t think of anything that better accomplishes both than a little bit of sentence correction.

Unless you were a big reader in high school (or you’re a incorrigible grammar nerd, the type who brightens up when I use the word “incorrigible”), sentence correction is probably your least favorite part of the GMAT. You should know English, you do know English, but the GMAT wants you to feel like you don’t, and it’s amazing the rest of us can even find the will to live while we listen to you talk. It wasn’t bad enough for the test writers to undo years of hard work with your therapist to forget your high school math; now they’re making you feel inadequate about your own language (or in some cases, a language you busted your butt to learn as an adult).

Like it or not, however, that’s the game here: testing the subtle differences between everyday English, the sort you speak and type and are reading from me right now (“This is him! Who were you looking for?”), and black-tie, formal English, the kind you use to lose friends and alienate people (“This is he! For whom were you looking?”). And no word — see how I started that sentence with “and”? I’m on your side! — better stands for this distinction than “which”, a seemingly simple, everyday word that you and the GMAT test writers will be fighting a brutal war to control.

In your world, after all, “which” is used to describe anything. In your world, “He was being such a jerk, which was totally uncalled for,” or, “I took the GMAT this morning, which was the worst thing I’ve done since I felt off the stage in the first act of that school play,” are perfectly grammatical. In the GMAT’s world, however, they aren’t, and it’s all because of that “which”. In your world, “which” can describe the gist of the sentence, but in the GMAT’s world, it describes the noun that precedes it. Luckily, there’s an easy, 99% accurate way to test GMAT-approved usage of “which”:

CORRECT: (non-human noun), which (phrase describing that noun)

INCORRECT: almost anything else

So these are correct:

“The sun, which is actually a star, was once considered a god.”

“My car, which has multiple dents, two differently colored front doors, and a dog sleeping on it, is a bit of a fixer-upper.”

“I finally saw Wayne’s World 2, which I’ve been hearing about for years.”

In each case, “which” directly connects a noun to a phrase that describes that noun. The sun IS actually a star, my car DOES have multiple dents, and Wayne’s World 2 WAS what I’d been hearing about (I’ve been living under a rock since 1992).

As obnoxious as this rule is — and by no means do I encourage you to follow it in your own writing or speech — it’s easy to remember on test day. If you see “which” begin a modifier, make sure that it’s next to the noun it describes. If it is, lovely! If it isn’t, burn that which!

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube and Google+, and Twitter!

Quarter Wit, Quarter Wisdom: The Tricky Critical Reasoning Conclusion

Quarter Wit, Quarter WisdomAs discussed previously, the most important aspect of a strengthen/weaken question on the GMAT is “identifying the conclusion,” but sometimes, that may not be enough. Even after you identify the conclusion, you must ensure that you have understood it well. Today, we will discuss the “tricky conclusions.”

First let’s take a look at some simple examples:

Conclusion 1: A Causes B.

We can strengthen the conclusion by saying that when A happens, B happens.

We can weaken the conclusion by saying that A happened but B did not happen.

How about a statement which suggests that “C causes B,” or, “B happened but A did not happen”?

Do these affect the conclusion? No, they don’t. The relationship here is that A causes B. Whether there are other factors that cause B too is not our concern, so whether B can happen without A is none of our business.

Conclusion 2: Only A Causes B.

This is an altogether different conclusion. It is apparent that A causes B but the point of contention is whether A is the only cause of B.

Now here, a statement suggesting, “C causes B,” or, “B happened but A did not happen,” does affect our conclusion. These weaken our conclusion – they suggest that A is not the only cause of B.

This distinction can be critical in solving the question. We will now illustrate this point with one of our own GMAT practice questions:

Two types of earthworm, one black and one red-brown, inhabit the woods near the town of Millerton. Because the red-brown worm’s coloring affords it better camouflage from predatory birds, its population in 1980 was approximately five times that of the black worm. In 1990, a factory was built in Millerton and emissions from the factory blackened much of the woods. The population of black earthworms is now almost equal to that of the red-brown earthworm, a result, say local ecologists, solely stemming from the blackening of the woods.

Which of the following, if true, would most strengthen the conclusion of the local ecologists?

(A) The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.

(B) The birds that prey on earthworms prefer black worms to red-brown worms.

(C) Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.

(D) The average life span of the earthworms has remained the same since the factory began operations.

(E) Since the factory took steps to reduce emissions six months ago, there has been a slight increase in the earthworm population.

Let’s look at the argument.

Premises:

  • There are two types of worms – Red and Black.
  • Red has better camouflage from predatory birds, hence its population was five times that of black.
  • The factory has blackened the woods and now the population of both worms is the same.

Conclusion:

From our premises, we can determine that the blackening of the woods is solely responsible for equalization of the population of the two earthworms.

We need to strengthen this conclusion. Note that there is no doubt that the blackening of the woods is responsible for equalization of populations; the question is whether it is solely responsible.

(A) The number of red-brown earthworms in the Millerton woods has steadily dropped since the factory began operations.

Our conclusion is that only the blackening of the woods caused the numbers to equalize (either black worms are able to hide better or red worms are not able to hide or both), therefore, we need to look for the option that strengthens that there is no other reason. Option A only tells us what the argument does anyway – the population of red worms is decreasing (or black worm population is increasing or both) due to the blackening of the woods. It doesn’t strengthen the claim that only blackening of the woods is responsible.

(B) The birds that prey on earthworms prefer black worms to red-brown worms.

The fact that birds prefer black worms doesn’t necessarily mean that they get to actually eat black worms. Even if we do assume that they do eat black worms over red worms when they can, this strengthens the idea that “the blackening of the woods is responsible for equalization of population,” but does not strengthen the idea that “the blackening of the woods is solely responsible for equalization,” hence, this is not our answer.

(C) Climate conditions since 1990 have been more favorable to the survival of the red-brown worm than to the black worm.

Option C tells us that another factor that could have had an effect on equalization (i.e. climate) is not responsible. This strengthens the conclusion that better camouflage is solely responsible – it doesn’t prove the conclusion beyond doubt, since there could be still another factor that could be responsible, but it does discard one of the other factors. Therefore, it does improve the probability that the conclusion is true.

(D) The average life span of the earthworms has remained the same since the factory began operations.

This option does not distinguish between the two types of earthworms. It just tells us that as a group, the average lifespan of the earthworms has remained the same. Hence, it doesn’t affect our conclusion, which is based on the population of two different earthworms.

(E) Since the factory took steps to reduce emissions six months ago, there has been a slight increase in the earthworm population.

Again, this option does not distinguish between the two types of earthworms. It just tells us that as a group, the earthworm population has increased, so it also does not affect our conclusion, which is based on the population of two different earthworms.

Therefore, our answer is C.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on FacebookYouTube and Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Movember and Moving Your GMAT Score Higher

GMAT Tip of the WeekOn this first Friday of November, you may start seeing some peach fuzz sprouts on the upper lips of some of your friends and colleagues. For many around the world, November means Movember, a month dedicated to the hopefully-overlapping Venn Diagram of mustaches and men’s health. Why – other than the fact that this is a GMAT blog – do we mention the Venn Diagram?

Because while the Movember Foundation is committed to using mustaches as a way to increase both awareness of and funding for men’s health issues (in particular prostate and testicular cancer), many young men focus solely on the mustache-growth facet of the month. And “I’m growing a mustache for Movember” without the fundraising follow-through is akin to the following quotes:

“I’m growing a mustache for Movember.”

“I’m running a marathon for lymphoma research.”

“I’m dumping a bucket of ice water over my head on Facebook.”

“I’m taking a GMAT practice test this weekend.”/”I’m going to the library to study for the GMAT.”

Now, those are all noble sentiments expressed with great intentions. But another thing they all have in common is that they’re each missing a critical action step in their mission to reach their desired outcome. Growing a mustache does very little to prevent or treat prostate cancer. Running a marathon isn’t what furthers scientists’ knowledge of lymphoma. Dumping an ice bucket over your head is more likely to cause pneumonia than to cure ALS. And taking a practice test won’t do very much for your GMAT score.

Each of those actions requires a much more thorough and meaningful component. It’s the fundraising behind Movember, Team in Training, and the Ice Bucket Challenge that advances those causes. It’s your effort to use your mustache, sore knees, and Facebook video to encourage friends and family to seek out early diagnosis or to donate to the cause. And it’s the follow-up to your GMAT practice test or homework session that helps you increase your score.

This weekend, well over a thousand practice tests will be taken in the Veritas Prep system, many by young men a week into their mustache growth. But the practice tests that are truly valuable will be taken by those who follow up on their performance, adding that extra step of action that’s all so critical. They’ll ask themselves:

Which mistakes can I keep top-of-mind so that I never make them again?

How could I have budgeted my time better? Which types of problems take the most time with the least probability of a right answer, and which types would I always get right if I just took the extra few seconds to double check and really focus?

Based on this test, which are the 2-3 content areas/question types that I can markedly improve upon between now and my next practice test?

How will I structure this week’s study sessions to directly attack those areas?

And then they’ll follow up on what they’ve learned, following the new week’s plan of attack until it’s time to again take the first step (a practice test) with the commitment to take the substantially-more-important follow-up steps that really move the needle toward success.

Taking a practice test and growing a Movember mustache are great first steps toward accomplishing noble goals, but in classic Critical Reasoning form, premise alone doesn’t guarantee the conclusion. So make sure you don’t leave the GMAT test center this November with an ineffective mustache and a dismal score – put in the hard work that has to accompany that first step, and this can be a Movember to Remember.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube, Google+ and Twitter!

By Brian Galvin.

The Critical Role of Reading in GMAT Critical Reasoning Questions!

Quarter Wit, Quarter WisdomMost non-native English users have one question: How do I improve my Verbal GMAT score?  There are lots of strategies and techniques we discuss in our books, in our class and on our blog. But one thing that we seriously encourage our students to do (that they need to do on their own) is read more – fiction, non fiction, magazines (mind you, good quality), national dailies, etc. Reading high quality material helps one develop an ear for correct English. It is also important to understand the idiomatic usage of English, which no one can teach in the class. At some time, most of us have thought how silly some things are in the English language, haven’t we?

For example:

Fat chance” and “slim chance’”mean the same thing – Really? Shouldn’t they mean opposite things?

But “wise man” and “wise guy” are opposites – Come on now!

A house burns up as it burns down and you fill in a form by filling it out?

And let’s not even get started on the multiple unrelated meanings many words have – The word on the top of the page, “critical,” could mean “serious” or “important” or “inclined to find fault” depending on the context!

Well, you really must read to understand these nuances or eccentricities, if you may, of the English language. Let’s look at an official question today which many people get wrong just because of the lack of familiarity with the common usage of phrases in English. But before we do that, some quick statistics on this question – 95% students find this question hard and more than half answer it incorrectly. And, on top of that, it is quite hard to convince test takers of the right answer.

Some species of Arctic birds are threatened by recent sharp increases in the population of snow geese, which breed in the Arctic and are displacing birds of less vigorous species. Although snow geese are a popular quarry for hunters in the southern regions where they winter, the hunting season ends if and when hunting has reduced the population by five percent, according to official estimates. Clearly, dropping this restriction would allow the other species to recover.

Which of the following, if true, most seriously undermines the argument?

(A) Hunting limits for snow geese were imposed many years ago in response to a sharp decline in the population of snow geese.

(B) It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.

(C) The number of snow geese taken by hunters each year has grown every year for several years.

(D) As their population has increased, snow geese have recolonized wintering grounds that they had not used for several seasons.

(E) In the snow goose’s winter habitats, the goose faces no significant natural predation.

As usual, let’s start with the question stem – “… most seriously undermines the argument”

This is a weaken question. The golden rule is to focus on the conclusion and try to weaken it.

Let’s first understand the argument:

Snow geese breed in the Arctic and fly south for the winter. They are proliferating, and that is bad for other birds. Southern hunters reduce the number of geese when they fly south. There is a restriction in place that if the population of the geese that came in reduces by 5%, hunting will stop. So if 1000 birds flew south and 50 were hunted, hunting season will be stopped. The argument says that we should drop this restriction to help other Arctic birds flourish (conclusion), then hunters will hunt many more geese and reduce their numbers.

What is the conclusion here? It is: “Clearly, dropping this restriction would allow the other species to recover.”

You have to try to weaken it, i.e. give reasons why even after dropping this restriction, it is unlikely that other species will recover. Even if this restriction of “not hunting after 5%” is dropped and hunters are allowed to hunt as much as they want, the population of geese will still not reduce.

Now, first look at option (B);

(B) It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.

What does this option really mean?

Does it mean the hunting season has been closing earlier than the scheduled date for many years? Or does it mean the exact opposite, that the restriction came into effect many years ago and since then, it has not come into effect.

It might be obvious to the native speakers and to the avid readers, but many non-native test takers actually fumble here and totally ignore option (B) – which, I am sure you have guessed by now, is the correct answer.

The correct meaning is the second one – the restriction has not come into effect for many years now. This means the restriction doesn’t really mean much. For many years, the restriction has not caused the hunting season to close down early because the population of geese hunted is less than 5% of the population flying in. So if the hunting season is from January to June, it has been closing in June, only, so even if hunters hunt for the entire hunting season, they still do not reach the 5% of the population limit (Southern hunters hunt less than 50 birds when 1000 birds fly down South).

Whether you have the restriction or not, the number of geese hunted is the same. So even if you drop the restriction and tell hunters that they can hunt as much as they want, it will not help as they will not want to hunt geese much anyway. This implies that even if the restriction is removed, it is likely that there will be no change in the situation. This definitely weakens our conclusion that dropping the restriction will help other species to recover.

So when people ignore (B), on which option do they zero in? Some fall for (C) but many fall for (D). Let’s look at all other options now:

(A) Hunting limits for snow geese were imposed many years ago in response to a sharp decline in the population of snow geese.

This is out of scope to our argument. It doesn’t really matter when and why the limits were imposed.

(C) The number of snow geese taken by hunters each year has grown every year for several years.

This doesn’t tell us how dropping the restriction would impact the population of geese, it just tells us what has happened in the past – the number of geese hunted has been increasing. If anything, it might strengthen our conclusion if the number of geese hunted is close to 5% of the population. When the population decreases by 5%, if the restriction is dropped, chances are that more geese will be hunted and other species will recover. We have to show that even after dropping the restriction, the other species may not recover.

(D) As their population has increased, snow geese have recolonised wintering grounds that they had not used for several seasons.

With this answer choice, “wintering grounds” implies the southern region (where they fly for winter). In the South, they have recolonised regions they had not occupied for a while now, which just tells you that the population has increased a lot and the geese are spreading. It doesn’t say that removing the restrictions and letting hunters hunt as much as they want will not help. In fact, if anything, it may make the argument a little stronger. If the geese are occupying more southern areas, hunting grounds may become easily accessible to more hunters and dropping hunting restrictions may actually help more!

(E) In the snow goose’s winter habitats, the goose faces no significant natural predation.

We are concerned about the effect of hunting, thus natural predation is out of scope.

Therefore, our answer is (B).

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube and Google+, and Twitter!

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

GMAT Tip of the Week: Trick or Treat

ZombieinsteinOne of the most dreaded things about the GMAT is the time-honored “Testmaker Trick” – the device that the GMAT question author uses to sucker you into a trap answer on a question. You’ve done all the math right, but forgot to consider negative numbers or submitted the answer for x when the question really asks for y. The “Testmaker Tricks” are enough to make you resent the test and to see it in a derogatory light. This is a grad school test, not Simon Says! Why should it matter that Simon didn’t say “positive”?

But as we head into Halloween weekend, it’s an appropriate time for you to think back to the phrase that earned you pounds and pounds of candy (and maybe tons if you followed Jim Harbaugh’s double-costume strategy): Trick or Treat.

In a GMAT context, that means that on these challenging questions, what tricks one examinee is the “treat” or reward for those who buy into the critical thinking mindset that the GMAT is set up to reward. The GMAT testmakers themselves are defensive about the idea of the “trap” answer, preferring to see it as a reward system; the intent isn’t to “trick” people as much as it is to “treat” higher-order thinking and critical reasoning. Consider the Data Sufficiency example:

Is x > 3z?

(1) x/z > 3

(2) z > 0

Here the “trick” that the testmaker employs is that of negative numbers. Many people will say that Statement 1 is sufficient (just multiply both sides by z and Statement 1 directly answers the questions, x > 3z), but it’s important to remember that z could be negative, and if it were negative you’d have to flip the sign, as you do in an inequality problem when you multiply or divide by a negative. In that case x < 3z and the answer is an emphatic no.

Now, those test takers who lament the trick after getting it wrong are somewhat justified in their complaint that “you forgot about negatives!” is a pretty cheap trick. But that’s not the entire question: Statement 2 exists, too, and it’s a total throwaway when you consider it alone. Why is it there? It’s there to “treat” those who are able to leverage that hint: why would it matter if z is greater than 0? That statement provides a very important clue as to how you should have been thinking when you looked at Statement 1.

If your initial read of Statement 1 – under timed pressure in the middle of a test, mind you – had you doing that quick algebra and making the mistake of saying that it’s sufficient, that’s understandable. But if you blew right past the clear hint in the second statement, you missed a very important opportunity to seize the treat. To some degree this problem is about the math, but the GMAT often adds that larger degree of leveraging hints – after all, much of business success comes down to your ability to find an asset that others have overlooked, or to get more value out of an asset than anyone else could.

So as you study for the GMAT, keep that Halloween spirit close by. When you miss a problem because of a dirty “trick,” take a second to also go back and see if you missed a potential treat – a reward that the GMAT was dangling just out of reach so that only the most critical thinkers could find it and take advantage. GMAT problems aren’t all ghosts, goblins, and ghouls out to frighten and trick you; often they include very friendly pieces of information just disguised or camouflaged enough that you have to train yourself to spot the treat.

Getting ready to take the GMAT? We have free online GMAT seminars running all the time. And, be sure to follow us on Facebook, YouTube and Google+, and Twitter!

By Brian Galvin.

Does the GMAT Even Really Measure Anything?

SAT/ACTAt some point, in pretty much every class I teach, a student will ask me what the GMAT really measures. The tone of the question invariably suggests that the student doesn’t believe that the test accurately assesses anything of real significance, that the frustrations and anxieties we endure when preparing for the exam are little more than a form of admissions sadism.

When it comes to standardized testing, a certain amount of cynicism is understandable – if person A has a better grasp on the fundamentals of geometry and algebra than person B, why on earth would we conclude on that basis that person A will be more likely to have a successful career in a field totally unrelated to geometry and algebra?

Of course, I have my stock answer: the test is designed to reward flexible thinking, to provide feedback on our ability to make good decisions under pressure. And though I do believe this, I’m also well aware that tests have their limitations. There are many incredibly talented and intelligent people who struggle in the artificial conditions of a testing environment, and no 3.5 hour exam will be able to fully capture an individual’s potential. At some level, we all know this. It’s why the admissions process is holistic. Still, your GMAT score is important, so I thought it worthwhile to do a bit of research about what the data says regarding how well the test predicts future success.

In 2005, GMAC issued a report in which it examined data from 1997-2004 about the correlation between GMAT scores and graduate school grades. The report summarizes a regression analysis in which researchers generated what they term a “validity coefficient.” A coefficient of “1” would mean that the correlation between the GMAT and graduate school grades was perfect – the two variables would move in lockstep. According to this report, any coefficient between .3 and .4 is considered useful for admissions.

The GMAT’s validity coefficient came out to .459, suggesting that the test does, in fact, have some predictive value, and this predictive value seems to be superior to other variables that admissions committees consider. The validity coefficient for undergraduate grades, for example, was .283. (And when the variables are combined, the validity coefficient is higher any individual coefficient.) So is that the end of the story? Can I rebuff my students’ complaints about standardized testing by sending them an abstract of this report? It’s not quite that simple.

In the conclusion section of the paper, we’re offered the following: “When examining the validity data in this study, one should recognize that there is a great deal of variability across programs and that the relative importance for each of the investigated variables differs for each program. This is to be expected.”

So one interpretation of the data is that the GMAT does a pretty good job of predicting how well students will do in their MBA programs. But if you’ve been studying for the GMAT for any length of time, hopefully your “correlation is not causation” reflex was triggered. What if students with higher GMAT scores attend more selective schools and then it turns out that those selective schools have more lenient grading policies because they figure that the necessary vetting has already been performed? In this case, the correlation between GMAT score and grades wouldn’t be shedding much light on how well the test-takers would perform academically, but rather, would be providing information about what kinds of programs test-takers would eventually attend.

Moreover, one could argue that looking at the correlation between GMAT scores and grad school grades is of limited usefulness. Schools no doubt hope their students do well in their classes, but it stands to reason that admissions decisions are also informed by predictions about what prospective students can contribute to the school’s community, as well as what kind of future career success these students can expect after they graduate. What, then, is the correlation between graduate grades and career success beyond the classroom? And how would we even begin to measure or define “success”? These are complex questions with no good answer.

Furthermore, while the paper appeared statistically rigorous to me, amateur that I am, we still have to consider that it was commissioned by GMAC, the company that administers the test, so there is a conflict of interest to bear in mind.  A recent article by the Journal of Education for Business questioned the results of the earlier research and insisted that the section of the GMAT that best predicted conventional managerial qualities, such as leadership initiative and communication skill, was the Analytical Writing section, the component of the test that admissions committees care about least and that had the lowest validity coefficient, according to the earlier paper.

Needless to say, though I found these papers interesting, they provided me with no definitive answers to offer my students when they ask about what the GMAT really measures. And, paradoxically enough, this is something we should find encouraging. If the GMAT were measuring any kind of fixed inherent quality, there’d be little point in prepping for the test. But if the test requires a unique skillset, that skillset can be mastered, irrespective of how directly applicable that skillset will be to future endeavors. Pragmatically speaking, the thing that matters most is that admissions committees do care about the GMAT score. So my ultimate message to my students is this: stop worrying about what the GMAT measures, and instead, harness that energy to focus on what you need to do to maximize your score.

Plan on taking the GMAT soon? We have GMAT prep courses starting all the time. And, be sure to find us on Facebook, YouTube and Google+, and follow us on Twitter!

By David Goldstein, a Veritas Prep GMAT instructor based in Boston. You can find more articles by him here.