GMAT Tip: Answer Clues Hidden in Plain Sight

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This tip on improving your GMAT score was provided by Brian Galvin at Veritas Prep.

The section of the GMAT that strikes the most fear into the hearts of Americans is the quantitative section. The curve is being set overseas, and the competition is steep. Two percent of all examinees hit the top score of 51, while a full 17 percent score 49 or higher—more evidence that it’s crowded at the top of the quant section and there’s not a huge margin for error.

Data-sufficiency questions supply two statements and offer five answer choices—A through E—that require test takers to determine whether one or both statements, alone or together, are sufficient to answer the question. So many prospective MBAs are surprised to learn that some of the most challenging and often-missed portions of these problems aren’t really all that mathematical. Often people miss these items because they’re looking too hard to “do math” and not hard enough at qualitative analysis of what the problems are really saying. Consider a few examples:

What is the value of x?

(1)  x2 = 16

(2)  6

In this version, neither statement alone is sufficient. Statement 1 allows for either -4 or 4, and statement 2 allows for any value between 3 and 5: maybe 4, but maybe 4.99999. Let’s add a couple “backstories” to the question to see how the GMAT can hide mathematical information where you’re not really looking for it.

Alternate Question Stem 1:  If x represents the number of fish in a fish tank, what is the value of x?

Alternate Question Stem 2: If x represents the number of gallons of water in a fish tank, what is the value of x?

To the naked eye, this nonmathematical information might seem superfluous, but in each case that information changes the answer to the question. For Alternate 1, the fact that x represents a number of fish means it cannot be negative (you can’t have -4 fish), making statement 1 (x2 = 16) sufficient. It also means x cannot be a noninteger—you can’t have 3.5 fish—so statement 2 (6

For Alternate 2, you can’t have negative water, so statement 1 is sufficient, but you can have 3.5 gallons of water, so statement 2 is not.

What’s important to recognize here is that the nonmathematical information in either of the alternate questions is paramount—that’s where the difficulty in the question lies. The GMAT is quite adept at hiding information in plain sight, knowing that people are in such a rush to get calculating that they overlook pertinent, more-logical-than-mathematical information.

So consider another question:

Four workers from an international charity were selling shirts at a local event yesterday. Did one of the workers sell at least three shirts yesterday at the event?

(1) Together they sold 8 shirts yesterday at the event.

(2) No two workers sold the same number of shirts.

This question is live in the Veritas Prep Question Bank, with more than 500 responses from GMAT students. And the statistics should prove the point of this article pretty dramatically: About half of all respondents pick the trap answer C (both statements together are sufficient but neither alone is sufficient), while only about 20 percent select the correct answer.

Here’s how they do it: Statement 1 is more mathematical, so they’ll look at it in an equation: a + b + c + d = 8, and since there are no constraints on the individual variables, they’ll see 2 + 2 + 2 + 2 = 8 as an obvious “no one sold at least three” answer. But if you take a shirt away from any one of the individuals you have to allocate it to another, meaning that unless they all sold two, someone sold three or more. So statement 1 is not sufficient … but it’s close.

Then when statement 2 comes along and rules out the 2 + 2 + 2 + 2 = 8 possibility, test takers may not give statement 2 more than a passing glance, but they realize it supplies that last piece of missing information from statement 1. Statement 2, along with 1, guarantees that someone sold at least three.

But here’s the catch: Statement 2 is not mathematical, really—you can’t turn it into an equation—but logically it is sufficient on its own. If all four people sold a different total, the minimum it could be is 0, 1, 2, and 3. Because you can’t double-up any numbers, there’s no way to take the fourth-highest total and make it anything less than 3. So statement 2 is sufficient on its own … it’s just “surprisingly sufficient” in that it doesn’t look like a math problem, so people don’t spend a ton of time on it.

So how can you use this to improve your GMAT quantitative score? Whether or not you’re a “quant” by nature, you need to recognize that nonmathematical information is critical on Data Sufficiency problems. Part of your goal on those questions should be to pay attention to the qualitative information and see how you can logically transform it into limits on the question. Even though Data Sufficiency appears in the quantitative section, qualitative information is often a much bigger factor than you’d expect.

For more quantitative practice, visit the Veritas Prep GMAT question bank, where you can work through realistic GMAT questions and review detailed solutions.

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