This tip on improving your GMAT score was provided by Brian Galvin at Veritas Prep.
GMAT data-sufficiency problems, particularly yes/no questions, are some of the most deceptively simple on the test. But test-takers can do quite well on these problems if they employ a simple strategy. If you can use each of the statements provided to arrive at both a “no” and a “yes” answer to the question (NY), you’ve proven that the statement doesn’t give you enough information to answer the question definitively. So when you see a yes/no data-sufficiency problem, your goal should be to get to NY. Here’s what we mean:
Consider the question: Is x > y?
Two statements are provided:
(1) x/y > 1
(2) y = 12
The question comes with five answer choices, A through E, requiring test-takers to determine if one or both statements—alone or together—are sufficient to answer the question, or if both statements are insufficient and additional information is needed.
Statement 1 is a bit abstract, so you might want to put some concrete numbers into play to get a better feel for it. If you were to plug in x = 4 and y = 2, you’d satisfy that expression (4/2 is indeed greater than 1) and you’d get the answer “yes,” so you could confidently write the letter Y on your note board.
Now that you’ve gotten “Y,” your primary goal should be to find “N;” if you can do this, you’ll definitively prove that statement 1 is not sufficient to answer the question. To do so, you may need to consider some “unorthodox” numbers, but this strategy pushes you to do so. Under what conditions could x/y be greater than 1 but x be less than y? What if x were -4 and y were -2? That still gives you 4/2 > 1, but in that case x is less than y. You have your “no,” so now that you’ve found NY, you can rule out statement 1 as not sufficient.
Statement 2 should be easier to rule out (Y: x = 13; N: x = 11). And taken together, the statements rule out your “they’re both negative” way of getting to N, so the correct answer to this question is answer choice C: “Both statements together are sufficient, but neither statement alone is sufficient.”
More important, recognize that on yes/no questions, your goal with each statement should be to get one N and one Y so that you can prove a statement to be insufficient. By actively seeking out each of those answers, you’ll push yourself to try the unique/unorthodox types of numbers that tend to form the traps for so many test-takers, and you’ll pick numbers and perform mathematical work more efficiently. When a question asks a yes/no question, your goal should be to make it to NY. If you can make it there, you’ll be that much closer to a GMAT score that can help you make it anywhere—such as Cambridge, Mass., Palo Alto, Calif., or even New York, N.Y.
Brian Galvin has studied the GMAT full time since 2006 as the director of academic programs for Veritas Prep. He received a Masters in Education from the University of Michigan and is the proud owner of a 99th percentile GMAT score.
For more GMAT advice from Veritas Prep, watch “A Sure Way to Beat GMAT Data Sufficiency Problems”