GMAT Tip: 'Why' Can Be as Important as 'What'

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

There’s a modern fable about a mother waiting with her elementary school daughter at the pediatrician’s office, and the daughter asks out of the blue, “What is sex?”

Understandably, the mother becomes worried—How do I explain this to her lightly in language she’ll understand? Am I ready to have this conversation?—and gets ready to stammer out the best reply she can under pressure. But first she has to ask, “Why, what do you mean sweetheart?”

The daughter’s reply: “It says here M or F.  Am I an M or an F?”

And the lesson?  Before you answer a question, it’s helpful to know why it was asked. Whether you’re a mother at the doctor’s office or an aspiring MBA on the GMAT, it pays to think “why” and not just “what.” Consider this example:

The variable x is inversely proportional to the square of the variable y. If y is divided by 3a, then x is multiplied by which of the following?

(A) 1/9a

(B) 1/9a²

(C) 1/3a

(D) 9a

(E) 9a²

Now, on this problem, they’re not really asking, “can you square 3a?” or anything like that. Look at the answer choices—three are fractions and two are not, and all have variations of 9 and a or a² in them. This problem is asking, “Can you keep the fraction straight when you’re squaring and dividing?” more than it is asking, “Can you square the variable?”

With that knowledge, you now know where to be careful. The danger here will lie in whether you flip the fraction or not (from 1/9a to 9a or 1/9a² to 9a²).  And since you know that the algebra might be dangerous here, maybe it’s a good idea to try small numbers instead. If you call y = 3, then x = 1/9, and y/3a = 3/3a = 1/a.  And that “inversely proportional to the square” conversion for x will then be a².  So the difference between the two xs is that you multiply the first by 9a² to get to the second, and the answer is E.

More important is the takeaway: When you know that what they’re really testing is, “taking reciprocals is prone to algebraic error,” you can absorb that knowledge and answer differently. If the answer choices to a problem look something like the following, you know that it’s testing degrees of magnitude and not the mechanical calculation:

(A) .001

(B) .0001

(C) .010

Or

(A) 2.4 x 10⁵

(B) 2.4 x 10⁶

(C) 2.4 x 10⁷

Knowing the question is testing degrees of magnitude, you can focus your attention on that magnitude and/or on predicting the number of digits. If answer choices are spread far apart, they may well be testing estimation ability. And in any of these cases, you can use that knowledge to help you allocate your effort and focus. If you know why they’re asking the question, it helps you develop an appropriate answer.

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