GMAT Tip: Simplifying the GMAT's 'Hard' Math

The authors of the GMAT are masters at making basic math difficult Photograph by James Leynse/Corbis

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

As an aspiring graduate student, someone with an elite college degree and plans to tack on an even more prestigious graduate education, you’d likely be insulted if an admissions officer asked you to divide 11 by 4, right?

But here’s the catch: The GMAT does ask (essentially) that question frequently, and most test takers answer it incorrectly. How can that be? The authors of the GMAT are masters at making basic math difficult. Your job as a GMAT test taker is to learn those methods—to “think like the test maker”—and be prepared to combat them on test day.

Here’s an example. You know exactly what you’d do when dividing 11 by 4: 4 goes into 11 twice with 3 left over. But you’re probably so quick with that kind of math that you just go straight to 2.75. So how does the GMAT make this concept hard? By forcing you not only to use those intermediate steps—the remainder, mixed number, and conversion to decimal—but by making you “reverse-engineer” them. If your entire life you’ve known division from A to Z, the GMAT likes to start you in the middle (say, at M), take you to Z, and see if you can find your way back to M.

Here’s how the GMAT has tested this exact topic: When m is divided by n, the remainder is 14. If m/n = 65.4, what is the value of n?

(A)    14

(B)    27

(C)    35

(D)    42

(E)    45

Notice that while this problem is significantly more involved than “11 divided by 4,” it’s the same exact concept. This is “one number divided by another,” but instead of giving you those two numbers and asking you for the quotient/remainder, they give you the remainder and the quotient and ask you for one of the original numbers. How should you proceed? By taking account of how well you know the concept. If this were just “11 divided by 4,” you’d answer it this way:

11/4 = 2 remainder 3

11/4 = 2 and ¾  (take the remainder and divide it back over 4)

11/4 = 2.75

Then use that small-number parallel situation to test the concept. The question tells you that:

m/n = 65 remainder 14 (just as you saw above, the quotient always stays the same … the remainder affects only the decimal points)

m/n = 65 and 14/n

m/n = 65.4

So you should now see the process: You take the mixed number (2 and ¾, or 65 and 14/n), do the division on that fraction, and that becomes your decimal points. So 14/n = 0.4, and you can then solve for n = 35.

More important than just this problem is recognizing how the GMAT makes basic math look advanced—it tests you on the concept you’ve always known, but in a way you’ve likely never thought about it. Your remedy? Prove the concept to yourself with small numbers, then apply it to their abstract question or to large/unwieldy numbers.

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 “GMAT Tip: How Does the GMAT Make Elementary Math So Challenging?”

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