Jan
4
2013

# GRE Answer Choice Tricks, Part 2

Last week, I showed you one trick that the test makers use to “hide” right answers. Here’s a second:

By mathematical convention, square roots shouldn’t appear in the denominators of fractions. The GRE adheres to this convention, which means that the answer you come up with will sometimes look radically (*cough*) different from the credited answer. For example, you might solve a problem and get:

But when you look at the answer choices, that fraction won’t appear anywhere. The correct answer would actually be .

This is a scary moment for many of you, since apart from the radical, those two numbers don’t look anything alike! As always, don’t panic. When you get an answer that looks nothing like the choices and there are radicals involved, make sure you don’t have any radicals on the bottom of the fraction. If you do, great! That’s your problem, and it’s an easy one to fix. Multiply the top and bottom of the fraction by any radicals on the bottom — in this case, by the square root of 3 — to “clean up” the fraction:

Remember, when you multiply a radical by itself, the number doesn’t change — all that happens is the radical “pops off.” And now, the 6 on top cancels with the 3 on the bottom to get , the answer you can calmly and happily click on Test Day.

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#### About the Author: Boris Dvorkin

After picking up degrees in English and computer science from Case Western, Boris Dvorkin worked for six unfortunate months as a computer programmer before finding a home at Kaplan in May 2008. He is now a full-time GRE faculty member on-site and online, and he's worked on Kaplan's curriculum for the recent GRE revision. Boris was named Kaplan's Teacher of the Year for 2010. When he's not gushing about standardized test trivia, Boris enjoys playing obscure strategy board games, and is the proud owner of no less than three different board games about Portuguese spice merchants.