DAT Strategy Session

Quantitative Reasoning

Strategy: Picking Numbers

Picking numbers is a powerful alternative to solving problems by brute force. Rather than trying to work with unknown variables, you can pick concrete values for the variables. Any answer choice that does not work for the concrete values cannot be the correct answer.

Pick simple numbers to stand in for the variables. Next, try all the answer choices, ditching those that don't agree with the question information. Remember to keep the values you've picked for the variables constant throughout the problem. If more than one answer choice works, try different values. The correct choice must work for all possible numbers.

Consider the following example:

If a and b are odd integers, which of the following is an even integer?

A. a(b - 2)
B. ab + 4
C. (a + 2)(b - 4)
D. 3a + 5b
E. a(a + 6)

You can run through the answer choices quite quickly by using the picking numbers strategy. Try a = 3, b = 5. Only (D), 9 + 25 = 34 is even.

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