Breaking Down Changes in the New Official GMAT Practice Tests: Unit Conversions in Shapes

QuadrilateralRecently, GMAC released two more official practice tests. Though the GMAT is not going to test completely new concepts – if the test changed from year to year, it wouldn’t really be standardized – we can get a sense of what types of questions are more likely to be emphasized by noting how official materials change over time. I thought it might be interesting to take these practice tests and break down down any conspicuous trends I detected.

In the Quant section of the first new test, there was one type of question that I’d rarely encountered in the past, but saw multiple times within a span of 20 problems. It involves unit conversions in two or three-dimensional shapes.

Like many GMAT topics, this concept isn’t difficult so much as it is tricky, lending itself to careless mistakes if we work too fast. If I were to draw a line that was one foot long, and I asked you how many inches it was, you wouldn’t have to think very hard to recognize that it would be 12 inches.

But what if I drew a box that had an area of 1 square foot, and I asked you how many square inches it was? If you’re on autopilot, you might think that’s easy. It’s 12 square inches. And you better believe that on the GMAT, that would be a trap answer. To see why it’s wrong, consider a picture of our square:

 

 

 

 

 

We see that each side is 1 foot in length. If each side is 1 foot in length, we can convert each side to 12 inches in length. Now we have the following:

DG blog pic 2

 

 

 

 

 

Clearly, the area of this shape isn’t 12 square inches, it’s 144 square inches: 12 inches * 12 inches = 144 inches^2.

Another way to think about it is to put the unit conversion into equation form. We know that 1 foot = 12 inches, so if we wanted the unit conversion from feet^2 to inches^2, we’d have to square both sides of the equation in order to have the appropriate units. Now (1 foot)^2 = (12 inches)^2, or 1 foot^2 = 144 inches^2.  So converting from square feet to square inches requires multiplying by a factor of 144, not 12.

Let’s see this concept in action. (I’m using an older official question to illustrate – I don’t want to rob anyone of the joy of encountering the recently released questions with a fresh pair of eyes.)

If a rectangular room measures 10 meters by 6 meters by 4 meters, what is the volume of the room in cubic centimeters? (1 meter = 100 centimeters)

A) 24,000
B) 240,000
C) 2,400,000
D) 24,000,000
E) 240,000,000

First, we can find the volume of the room by multiplying the dimensions together: 10*6*4 = 240 cubic meters. Now we want to avoid the trap of thinking, “Okay, 100 centimeters is 1 meter, so 240 cubic meters is 240*100 = 24,000 cubic centimeters.”  Remember, the conversion ratio we’re given is for converting meters to centimeters – if we’re dealing with 240 cubic meters, or 240 meters^3, and we want to find the volume in cubic centimeters, we’ll need to adjust our conversion ratio accordingly.

If 1 meter = 100 centimeters, then (1 meter)^3 = (100 centimeters)^3, and 1 meter^3 = 1,000,000 centimeters^3. [100 = 10^2 and (10^2)^3 = 10^6, or 1,000,000.] So if 1 cubic meter = 1,000,000 cubic centimeters, then 240 cubic meters = 240*1,000,000 cubic centimeters, or 240,000,000 cubic centimeters, and our answer is E.

Alternatively, we can do all of our conversions when we’re given the initial dimensions. 10 meters = 1000 centimeters. 6 meters = 600 centimeters. 4 meters  = 400 centimeters. 1000 cm * 600 cm * 400 cm = 240,000,000 cm^3. (Notice that when we multiply 1000*600*400, we can simply count the zeroes. There are 7 total, so we know there will be 7 zeroes in the correct answer, E.)

Takeaway: Make sure you’re able to do unit conversions fluently, and that if you’re dealing with two or three-dimensional space, that you adjust your conversion ratios accordingly. If you’re dealing with a two-dimensional shape, you’ll need to square your initial ratio. If you’re dealing with a three-dimensional shape, you’ll need to cube your initial ratio. The GMAT is just as much about learning what traps to avoid as it is about relearning the elementary math that we’ve long forgotten.

*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 written by him here.

GMAT Tip of the Week: Your Mind Is Playing Tricks On You

GMAT Tip of the WeekOf all the song lyrics of all the hip hop albums of all time, perhaps the one that captures the difficulty of the GMAT the most comes from the Geto Boys:

It’s f-ed up when your mind is playing tricks on you.

The link above demonstrates a handful of ways that your mind can play tricks on you when you’re in the “fog of war” during the GMAT, but here, four Hip Hop Months later in the middle of yet another election season that has many Millennial MBA aspirants feeling the Bern, it’s time to detail one more. Consider this Critical Reasoning problem:

Among the one hundred most profitable companies in the United States, nearly half qualify as “socially responsible companies,” including seven of the top ten most profitable on that list. This designation means that these companies donate a significant portion of their revenues to charity; that they adhere to all relevant environmental and product safety standards; and that their hiring and employment policies encourage commitments to diversity, gender pay equality, and work-life balance.

Which of the following conclusions can be drawn based on the statements above?

(A) Socially responsible companies are, on average, more profitable than other companies.
(B) Consumers prefer to purchase products from socially responsible companies whenever possible.
(C) It is possible for any company to be both socially responsible and profitable.
(D) Companies do not have to be socially responsible in order to be profitable.
(E) Not all socially responsible companies are profitable.

How does your mind play tricks on you here? Check out these statistics from the Veritas Prep Practice Tests:

Socially responsible

When you look at the two most popular answer choices, there’s a stark difference in what they mean outside the context of the problem. The most popular – but incorrect – answer says what you want it to say. You want social responsibility to pay off, for companies to be rewarded for doing the right thing. But it’s the words that don’t appeal to your heart and/or conscience that are the most important on these problems, and the justification for “any company” to be both socially responsible and profitable isn’t there in the argument.

Sure, several companies in the top 10 and top 100 are both socially responsible and profitable, but ANY company means that if you pick any given company, that particular company has to be capable of both. And it may very well be that in certain industries, the profit margins are too slim for that to be possible.

Say, for example, that in one of the commodities markets there simply isn’t any brand equity for social responsibility, and the top competitors are so focused on pushing out competition that any cost outside of productivity would put a company into the red. It’s not a thought you necessarily want to have, but it’s a possible outcome given the prompt, and it invalidates answer (C). Since Inference answers MUST BE TRUE, C just doesn’t meet that standard.

Which brings you to D, the correct but unpopular answer. That’s not what your heart and conscience want to conclude at all – you’d love for there to be a world in which consumers will reject any products from companies that aren’t made by companies taking the moral high ground, but if you look specifically at the facts of the argument, 3 of the top 10 most profitable companies and more than half of the top 100 are not socially responsible. So answer choice D is airtight – it’s not what you want to hear, but it’s definitely true based on the argument.

The lesson? Once you get that MBA you have the opportunity to change the world, but while you’re in the GMAT test center doing Critical Reasoning problems, you can only draw conclusions based on the facts that they give you. Don’t let your outside opinions frame the way that you read the problem. If you know that you have some personal interest in the topic, that’s a sign that you’ll need to be even more literal about what’s written. Your mind can play tricks on you – as it did for nearly half of test-takers here – so know that on test day you have to get it under control.

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By Brian Galvin.

Success Story Part 3: "The Final Days, and (*eek*)… Results."

(This is the third in a series of blog posts in which Julie DeLoyd, a Veritas Prep GMAT alumna-turned-instructor, will tell the story of her experience through the MBA admissions process. Julie will begin her MBA program at Chicago Booth this fall. You can also read Part 1 and Part 2 to learn Julie’s whole story.)

I had invested 42 hours of summer evenings learning about the ins and outs of the GMAT, and the time finally came for me to do the work on my own. I booked my test date for 5 weeks after my class ended, giving me enough time to go on tour one last time before I really hunkered down.

My band toured the Midwest for about 10 days, driving on vegetable oil fuel and breaking a lot of strings along the way. While another girl was driving, I’d pull out my Veritas Prep books and work on a few problems each day. I wasn’t absorbing too much, honestly, but it was good to keep my GMAT brain active. When I dropped off the girls at the airport, it was time to really get down to business. I set up a study schedule for myself for the last 3 weeks.

21 days to go, with 4 practice tests completed, my schedule looked something like this:
Monday Morning: Sentence Correction
Monday Afternoon: Practice Test

Tuesday Morning:
Go over results of Practice Test
Tuesday Afternoon: Geometry

Wednesday Morning:
Reading Comp
Wednesday Afternoon: Practice test

Thursday Morning:
Go over results of Practice Test
Thursday Afternoon: Critical Reasoning

Friday Morning: Combinatorics and Probability
Friday Afternoon: Problem Solving

Saturday Morning: Practice Test
Saturday Afternoon: Go over results

Sunday: Eat good food, Ride my bike, Spend time with dogs and lovey

Yes, it was a little intense, but it wasn

GMAT Tip of the Week

Make No Mistake

(This is one of a series of GMAT tips that we offer on our blog.)

If you’re serious about GMAT preparation, you have undoubtedly taken (or will take) a series of practice tests to replicate the test experience and work on pacing, stamina, etc. (At Veritas Prep, we offer our students 15 CAT exams, and you can access a free GMAT practice exam on our web site). Most tests have some useful diagnostic features that will demonstrate the time you took on each question, your performance on major question categories, etc. But as you have read in this space previously, one true key to peak performance is to be aware of the errors that you tend to make in particular, and the software isn’t quite advanced enough to highlight those for you.

To better understand your own mistakes in your own way, a simple activity is to go back through 2-3 practice tests that you’ve taken and label each of your mistakes with 4-6 keywords of your own. Examples could include “Data Sufficiency, didn’t forget first statement” or “Strengthen argument, misread conclusion”. The tests themselves may alert you to the fact that you missed, say, 6 of 15 Data Sufficiency questions, but with closer inspection you can determine just which errors you’re making when you do miss them. Then, if you scan those keywords to find repeats (Microsoft Excel can do this pretty easily for you), you’ll have a better idea of just which mistakes you’re prone to making, and you can focus your attention on them.

Your strategy for GMAT success should certainly include become more comfortable with the various skills and question types required, but you’ll likely find that you can increase your score just as significantly by minimizing the errors you tend to make most commonly. Minimize your errors, and maximize your score!

More more help on the GMAT, take a look at Veritas Prep’s GMAT preparation course options.