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GRE Quantitative Comparison Continued

This article takes up from where the one of 9th March left off. Now we will take a look at QC questions from a slightly different perspective. The first three answer options can be modified by using “Always”.

The modified answer choices are as follows:

  1. Value of Column A is ALWAYS greater than the Value of Column B.
  2. Value of Column B is ALWAYS greater than the Value of Column A.
  3. Both the values of Column A and B are ALWAYS same.
  4. The relationship between values of Column A and B cannot be determined from the information provided.

Interestingly this small change justifies the significance of the last answer option (D), i.e. whenever we find a single possible case when the ALWAYS greater or ALWAYS equal thing can be negated! Students are seen hesitating to mark the answer option D; in fact, they make that extra effort to cross check before marking it and in the process waste time on a fairly futile task..

3] Look out for D!

What I mean by ‘look out for D’ is that the moment you see a Quantitative Comparison question involving variables, try to prove the answer D. The key is to look for numbers that would work differently from the previously used numbers. Let us take an example to elaborate this approach.

y=2x+5

Quantity A

Quantity B

x

y

Now in this question if we assume , then the value of , thus clearly quantity B is greater than that of quantity A. So the answer is B. But let us try some other number for x. Our intention here is to look out for any number which can negate our previous answer i.e. quantity B is greater. Ok, so if I just assume that both the quantities are equal, say we plug in the given equation:

Therefore, . So, what we get here is, when then both the quantities are equal i.e answer C. As quantity A is not Always greater, we cannot determine the exact relationship between quantity A and B, thus the answer is D!

Please try the following example using the above strategy:

q>1

Quantity A

Quantity B

Well, a very interesting fact about this method is that when we cannot find any number which negates the answer using a previous number, then the answer must be the previous one!

Let us take one example on this:

x=y+7

Quantity A

Quantity B

Now in this problem, if we assume that , we get Thus, quantity A is greater than B. Therefore answer A. Now we cannot find any single value of x which negates the above answer, hence the answer is 100% A.

We do have a couple of other methods such as “using Inequality concept” as this is a comparison question and “plug in values in variables” which help minimise the efforts in QC questions, but the above methods are most frequently useful in actual exam! All the Best! Do write in for any doubts.