Mastering GRE Quantitative Comparisons

January 2, 2014
Gene Suhir

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GRE Quantitative Comparison Tips

Use a strategic approach to Master GRE Quantitative Comparisons.
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Quantitative Comparisons have been a staple of the GRE for many years, and there is no sign of this changing anytime soon.  So any GRE student who hopes to be a GRE Test Day champion needs to master the GRE Quantitative Comparison question type and all its nuances. Doing so will allow you to rack up as many GRE points as possible, as quickly as possible, and as painlessly as humanly possible.

Out of 20 problems in each Quantitative section of the GRE, about 7 or 8 of them will be Quantitative Comparisons — certainly a pretty sizable chunk of your GRE Quant score that deserves your attention.

One upside to Quantitative Comparisons is that they follow a consistent pattern:  You are presented with two quantities — A and B. And the answer choices never change:

  • (A) is the answer if Quantity A is bigger than Quantity B.
  • (B) is the answer if Quantity B is bigger than Quantity A.
  • (C) is the answer when the quantities are equal in value, and
  • (D) is the answer if the relationship between the quantities cannot be determined.

The first step to conquering QCs is memorizing what these answer choices mean so that you don’t have to spend precious time reading them on Test Day.  And because there are only 4 answer choices, should you have to guess on a particular QC problem, your  probability of getting it right is 25% — higher than your probability of guessing correctly on Problem Solving questions, which have 5 answer choices.

This probability increases even more if each quantity contains only numbers (i.e., no variables), because in such a situation, you can certainly eliminate answer choice (D) and have a 33.33% chance of getting it right without even doing any math.

Practice Quantitative Comparison Problem

Quantity A Quantity B
37 + 38 + 39 310

When each quantity contains only numbers, there must be some constant relationship between them.  Either Quantity A is bigger, Quantity B is bigger, or they’re equal, but we know the relationship can be determined.  Hence, we eliminate (D).  Now where to proceed from here?  Even though there is an onscreen calculator available, there is actually a much more efficient shortcut.

The amateur test-taker would consider actually sitting there and multiplying out 37 (3 × 3 × 3 × 3 × 3 × 3 × 3), then doing the same thing with 38 , 39 , 310. This would not only end up sucking up a lot of time, but would also make it quite likely that he/she would make an arithmetic mistake because of dealing with…very technical term coming…Big Ugly Numbers (B.U.N.).  May the GRE Gods have mercy on the souls of people who try to do it this way!

On the other hand, the Kaplan-trained GRE test-taker instead uses two Kaplan principles of QCs:

  1. Compare, don’t calculate! 
  2. Make the quantities look alike so that you may easily compare them.

In Quantity A, you can factor out a 37 from each of those terms, because each of those terms has a 37 in it.  You get:

37 ( 1 + 31 + 32) = 37 (1 + 3 + 9) = 37 (13).

Now, to make Quantity B look similar, you must also factor out a 37, and we get 37 (33) = 37 (27).  We will be covering more on basics of exponent rules in a later blog entry, so stay tuned!  But you can now compare the two quantities piece-by-piece (another core Kaplan QC principle):

Quantity A Quantity B
37 (13) 37 (27)

Both quantities contain a 37 , but Quantity B’s “27” is larger than Quantity A’s “13,” and thus Quantity B is bigger, so the answer is (B).  Notice that you don’t actually have any idea as to what the actual value of either quantity multiplies out to. This is the type of strategic thinking that makes Kaplan-trained GRE students proceed without reservation, hesitation, or equivocation when they encounter a seemingly ugly Quantitative Comparison.

Ready to tackle more Quantitative Comparison questions? Check out another blog entry on this topic, where we cover additional GRE Quantitative Comparison tips to help guarantee your GRE Test Day success!

Gene Suhir Since 2002, Gene has been helping Kaplan GRE students become test-day champions. After graduating from the University of Maryland with a dual-degree in Political Science and Communications, Gene quickly set to work as one of Kaplan's best teachers. As an aficionado and master of all things test-prep, Gene's students agree that he not only helps demystify the GRE, but also makes studying for the test an enjoyable, and dare we say, fun experience as he coaches them towards GRE excellence. His expertise earned Gene an esteemed "Teacher of the Year" Award in 2006 and 2009 and has made him one of Kaplan's most requested GRE instructors. When he's not instilling Kaplan's proven test-day strategies to students around the world, Gene is an avid traveler, amateur magician, and guitar player. You can find Gene teaching GRE Classroom Anywhere or in the videos of GRE On Demand.

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