In Data Sufficiency, the GMAT is asking you to determine how much information is required to make a decision. If the information provided leads you a definite yes, then you have sufficient data to take decisive action. Similarly, if there is enough information to lead to a definite no, then you can also take decisive action. The only time trouble arises is when the information could lead to a yes or to a no; this situation leaves you in a position where you may have to guess (I’ll take Door #1, Bob).
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The holiday season is upon us in much of the world, and in the U.S. there is a special holiday this year called “Thanksgivikkah!” This is a combination of the words “Thanksgiving” and “Hanukkah” (The first full day of Hanukkah happens to be on November 28th this year – the same day as Thanksgiving in the U.S. This has never happened before and will not happen again in any of our lifetimes).
When evaluating critical reasoning questions, you often notice multiple answer choices that all seem plausible. The GMAT testmakers are experts at creating answer choices that are plausible and could potentially be correct, given slightly different circumstances. When evaluating strengthen or weaken questions, it is best to predict an answer from the stimulus before looking at the answer choices. That way you won’t be swayed by logical but out of scope questions (plus it’s a surprise!)
The GMAT is not merely a test for graduate school. Several very valuable qualities of the mind, useful in the course of human life, are to be acquired or strengthened by it, so as to become habits, ready on all occasions. Let’s examine a few of these qualities:
1. Decisiveness, which looks at the information and question, and considers the best course of action; for it occurs to the test taker, ‘how can I break this down into something I can figure out quickly? What is the situation and question really getting at? Can I ballpark or use the answer choices to narrow it down? How much time is worth spending to get this?’
Last week, we introduced the idea of “mirroring” in data sufficiency, and this week we’ll continue on that subject and look at different types of mirrors. “Mirroring” is my way of speaking about a technique called “manipulate algebraically” where the test taker attempts to manipulate either the statement or the question itself (or both) in order to get those statements to match each other exactly.
One of the most important concepts on the GMAT quant section is the notion of factors. Because there is no calculator on the exam, the multiplications and divisions tend to heed integer numbers. Dividing 100 by 2 might be trivial, but dividing 1100 by 22 might hinge on your recognition of the common factor of 11 to avoid tedious and time-consuming calculations.
In the Veritas Prep Data Sufficiency book, we have a section called the “Data Sufficiency Toolkit.” This toolkit contains a technique called “Manipulate Algebraically.” This technique involves “manipulating” either the statement or the question stem (or both) so that they exactly match each other.
In many ways, critical reasoning questions best exemplify what the GMAT is all about. The exam is primarily an exercise in applying logic to various different situations. In the quant section, you must either find the correct answer or determine whether you have sufficient information to make a decision. On the verbal section, you must find the answer choice that logically completes the information given in the question stem. Even on the AWA and the IR, logic is again paramount to knowing how to proceed and getting a good score.
Critical Reasoning is more than just one of the three verbal sections on the GMAT. It’s a way of thinking that applies to every GMAT subject area. In fact, it’s more still. It’s a skill that has wide application outside the GMAT.
The classic example of a lack of critical reasoning is the groupthink that led to the mortgage crisis, which eventually caused the global financial crisis. Very few people questioned the assumption that house prices would continue to rise. As long as prices rose, homeowners would be able to refinance their mortgages when, for example, low introductory interest rates increased or when balloon payments came due. And the system would keep chugging along. But it didn’t…
Percentages represent one of the most underestimated question types on the GMAT quant section. Absolute numbers are helpful to give concrete information (I spent 70$ on the latest Grand Theft Auto game), but percentages give a better indication of relative amounts of time (I spend 68% of my free time playing GTA V). Based on the first, you may find that I overpaid for the video game, but based on the second statistic, I probably got a very good return on my investment.
As you are probably well aware, success on the quantitative section of the GMAT requires not only computational ability, but also test taking acumen. For example, the fact that you are capable of determining a particular quantity from the information given in a problem does not mean that it is necessarily in your best interest to do so. At this point, you may assume that what follows is a discussion of data sufficiency (DS) strategy.
Critical Reasoning questions on the GMAT are primarily about strengthening or weakening the author’s conclusion. The stimulus of the question will describe some event or issue and then purport some conclusion, often one that is strikingly unsupported by the evidence.
Your job is usually to determine which answer choice would either enhance or undermine the professed conclusion. Sometimes, the question asks you to infer something that must be true from the text. The answer choices for these inference questions tend to have very high standards to meet because they must be true at all times (and not just when the moon is in Aquarius).
When looking at geometry problems on the GMAT, it’s important to take all graphs with a grain of salt (low fat, though). The graphs used on the GMAT are simply there to help visualize the problem at hand. No concerted effort is made for the graphs to be accurate or exact, and the graph should be evaluated based on what you know to be true, not on what you see or what the graph seems to imply. This all means that trusting your eyes on the GMAT is like trusting a car mechanic: you may have an honest mechanic or you may be getting taken for a ride!
In Part I of Organizing Your Information, we talked about rate time distance problems. In this one, we’ll tackle the Grizzly Peak problem from the Veritas Prep Arithmetic homework. I can’t tell you how many questions have been asked about this one in office hours, or via email support.
It’s the first day of class, and students are volunteering what they think of the GMAT. The typical sentiment goes something like: “Tough!” “Tricky stuff, hard to get a grasp on the logic,” or “I like ___ but really have trouble with ___.” Some just have a knowing smile that says “yeah, it’s a clever exam, but I’ll be glad when it’s over.”
Some concepts on the GMAT are absolute, while others can be a little nebulous. For example, the fact that there are 37 quantitative questions and 41 verbal questions is uncontestable. However, not all issues are as cut and dry.
I’ve read a strategy guide that recommended spending extra time on the first 10 questions because they’re worth more. I’ve read other guides saying that all the questions are weighed equally. Of course none of these books are the Official Guide, but even when I put it down, you know I’ll be back. When studying for a known test like the GMAT, it’s important to know what to look for and what to avoid (and also to be literate).
I often have students who, in the first few weeks of the GMAT course, tell me they really can’t stand Data Sufficiency. They fall into a few different camps, but we’ll look at two primary ones.
First, we have our engineers and “number crunchers,” frustrated by Data Sufficiency because there’s no closure, so to speak, at the end. There’s truly something rewarding for a lot of us about grinding out a page of math and getting to an answer.
When looking at questions on the GMAT, it’s very easy to fall into the mentality that there is only one correct answer. If I’m searching for some number xyz multiplied by another number abc, I don’t necessarily know the answer, but I know there’s only one value that will correctly satisfy the equation. The entire concept of multiple choice is predicated on having only one correct answer (also on knowing the alphabet), so it seems counter-intuitive that two values could both be the correct answer.
So we all know the GMAT is a “hard” exam, but just how hard is it supposed to be? Less hard than climbing Mt. Everest? Well, it depends what type of climber you are. If you’re feeling overwhelmed about the GMAT and are hesitant about whether to even get started, let’s face a few home truths that will hopefully leave you feeling encouraged!
Did I just use “GMAT” and “fun” in the same sentence? While months of prepping for a standardized test may not sound like a weekend at Disneyworld, it doesn’t all have to be drudgery and disappointment. Here are some quick study ideas to make your GMAT sessions a little more entertaining.
In critical reasoning, several factors can give away a potential incorrect answer choice. If the question is asking you to strengthen or weaken the author’s argument, the correct choice must always provide new information that either reinforces the author’s main point or calls into question its validity. However, certain answer choices give the illusion of talking about the subject without really saying anything conclusive about it (what one of my former professors colorfully called hand waving).
While my personal preference is to use a Venn diagram when dealing with most Sets questions, there are some questions in which a double-matrix is necessary (and much more powerful than a wimpy Venn). This little guy will make even the scariest-looking Sets question into a simple set of rows and columns, and its ability to help us determine whether a statement is sufficient in DS is unmatched!
We tend to see a lot of plane geometry questions on the GMAT involving benches, walkways, or other additions being constructed “around” shapes. We’re usually given a few different parts (length, width, or radius) and then asked to find something like the new total area, the original perimeter, or the new length with the addition.
Of all the topics on the GMAT quant section, few get students as confused as the concept of combinatorics. The concept of going to the store and picking up one of four possible gifts for a niece is pretty straightforward (she generally likes Barbies© or My Little Pony© toys), but picking up two toys out of four for your twin nieces and then deciding which one gets which often deteriorates into an exercise of brute force combinatorics.
I don’t know about you, but when I see formulas for sets that look like P(A) + P(B) + P(C) – 2P(A n B) – 2P(A n C) – 2P(B n C) + 3P(A n B n C), it takes me a minute for my brain to recall exactly what all these signs and symbols mean.
Even if we’re die-hard GMAT-ers, we’re just not used to seeing that many sets questions on practice tests, so while we know n = intersection and u = union, these formulas are just not easy to recall or employ.
Quant questions on the GMAT occasionally ask us to find the length of the longest distance between two vertices in a rectangular solid. To solve these, usually we solve by (1) drawing the figure to visualize it, and (2) carefully applying the Pythagorean Theorem twice.
In a cube with a side length of 12 cm, A is the midpoint of an edge that lies on the base and B is the midpoint of a vertical edge. What is the greatest possible distance between A and B rounded to the nearest integer?
A quote often attributed to (2nd US President) John Adams states that “facts are stubborn things”. In everyday life, we are often confronted with various personal opinions or subjective viewpoints on everything from politics (more horses and bayonets or less?) to fashion (can you believe what Miley Cyrus wore last week) to love (you complete me). However everyone understands that personal opinions are, well, personal. They vary from one individual to another and two people can have completely different beliefs on the exact same issue.
The Discovery Channel’s “Shark Week” may have more thrills than the GMAT, but the jaws of those deadly sea-predators are a great inspiration to look at one of the GMAT’s own mysterious creatures: circles. Since we miss Shark Week around here, we give you “Arc Week” today.
When it comes to circles, most of us are old pros at finding the area and circumference, and setting up basic ratios and proportions with the parts of a circle, but there are several lesser-known theorems involving the arcs of a circle that might be helpful to have up your sleeve for a GMAT rainy day!
There is one recurring question everyone has about the GMAT: what can I expect on “Game Day” and how well will practice tests prepare me for the real deal? This is a tough question; everyone trains and reacts differently. However, there’s one thing you should know: The GMAT Will Surprise You. It will surprise you because the test makers want to hit you with difficult and unexpected challenges; it’s the best way to prove you earned the score.
When studying for the GMAT, some questions will undoubtedly bring back fond memories of high school math classes, cramming for exams and wondering if that classmate you had a crush on even knew you existed (note: this may also remind you of Dawson’s Creek). Algebra and Geometry concepts evoke these feelings of nostalgia, because unless you’re an engineer or an architect (perhaps Art Vandelay?), you probably haven’t thought about the concepts in a decade or two.
We’ve looked at a lot of ways the GMAT can make Data Sufficiency questions more challenging (number properties, I’m talking to you!), but one type of DS question the GMAT likes to throw out there to really confuse unwary test-takers are value questions that ask about sums.
Say we had a question that asked, “what is the value of the sum of x and y?” Immediately, we have two possible ways that the statements could offer sufficiency: if they provided us with the ability to solve for x and y independently, and if they provided us with the ability to find the sum itself.
On the GMAT quantitative section, you have just over 2 minutes on average to answer each question in front of you. Sometimes, those two minutes go by in a flash and you feel like the question should take at least 4 minutes in order to even make a reasonable guess. Other times, you think you can solve the question in a matter of seconds, and wonder why anyone would take a full 2 minutes on a question that you can eyeball without putting pen to paper (or marker to dry erase board). Because the 2 minute benchmark is an average, not a maximum, figuring out how much time to spend on each question is a crucial part of doing well on this test.
When reading through Reading Comprehension texts, there are a few important concepts to keep in mind in order to be able to swiftly answer the upcoming questions. Every passage will have explicit information regarding the subject matter at hand, but some information will come from the author’s attitude and writing style. One of the most important things to do while reading a Reading Comprehension passage (other than staying awake) is determine the author’s tone.
We introduced the most common sense way of approaching a simple work rate problem last week in Part I. No setup was necessary. There was zero possibility for a calculation error, or a misconception.
The past perfect tense in a GMAT Sentence Correction question can subtly change the meaning of a sentence, making an answer choice incorrect, even if the verb agrees with its subject in number. The past perfect tense is often used to describe an action that was completed prior to another past action:
Just as all roads lead to Rome (well, all roads in Europe anyways), there are many ways to solve math questions on the GMAT. Any question can conceivably be solved in a variety of ways, but they must always be logical. No method is inherently superior to any other, so often it’s a question of which method will solve this particular problem in the most efficient way possible.
Combined work rate problems give many a headache at their mere mention. After all, you have to think in terms of that fourth dimension, “time” (cue the Twilight Zone theme). This alone puts it up there with Einsteinian Relativity in terms of difficulty. There are always three moving parts – time, work, and speed – and sometimes three or more machines or people working together.
Many GMAT students have likened themselves to Sherlock Holmes at one point or another while studying for this test. It is a natural comparison: you are a detective looking for clues in order to reach a conclusion that must be true. Unfortunately there’s no Dr. Watson to help guide your efforts, but you can inspire yourself from the super sleuth in your quest to solve the nefarious puzzles of Professor G. MoriArTy.