McGraw-Hill Education GRE 2019

Though the choices on the test do not state it explicitly, your concern is whether

there is a constant relationship between the quantities. Specifically, if you can

determine that in some instances, Quantity A is greater, but in other instances,

Quantity B is greater, then the answer is Choice D: the relationship cannot be

determined. To choose A, B, or C, you need to show that the given relationship is

always true. Let’s look at a sample question:

QUANTITY A QUANTITY B

A B C D

Choose:

A if Quantity A is greater

B if Quantity B is greater

C if the two quantities are equal

D if the relationship between the two quantities cannot be determined

SOLUTION: If x is greater than 2, then Quantity A is always greater. For

example, if x = 3, then the value of Quantity A is 30, and the value of

Quantity B is 23. Thus you can eliminate choices B and C. Why? Because if

Quantity A is greater in this instance, then it is not possible for Quantity B

to always be greater or for the two quantities to always be equal. Now that

the choice is between A and D, determine whether Quantity A will always be

greater. Substitute 1 for x. Quantity A = 8, and Quantity B = 15. In this case,

Quantity B is greater. Since different values yield different relationships, the

relationship cannot be determined, so the correct answer is Choice D.

Strategy: Play Devil’s Advocate

The example question illustrates the type of reasoning fundamental to Quantitative

Comparison questions. The best way to think about the quantities is to ask

yourself: “Will this relationship always be true?” Often, it will turn out that the

value in one column is sometimes larger than the value in the other column, and

sometimes smaller than the value in the other column. In such cases, the answer

will be D, not A or B. For the answer on Quantitative Comparison to be A, B, or

C, that relationship must always be true. If you find contradictory relationships

between the columns, then the answer is Choice D.

As you might expect, many tougher Quantitative Comparison questions will

expect you to identify situations in which there is an indeterminate relationship

between the columns. To identify that this is the case, your ultimate goal should

be to arrive at Choice D! For example, if you determine that Quantity A is greater

in one situation, your next step should be to determine whether there are other

situations in which the relationship between the two quantities is different. Look at

the following examples:

x^2 + 7x x^2 + 14

162 PART 3 ■ GRE QUANTITATIVE REASONING

02-GRE-Test-2018_107-172.indd 162 13/05/17 11:06 am