GMAT Tip of the Week

A Pattern of Efficiency

(This is one of a series of GMAT tips that we offer on our blog.)

A colleague recently pointed out a practice test problem he had seen that appeared to be a unique, new variety of GMAT quantitative problem. (Editor’s note: There is no need for alarm; continue reading and you’ll learn that this problem is entirely common on the exam and has been for years!) The problem asked for the test taker to sum a relatively high number of values that were displayed on a grid; the extent of the problem was similar to:

What is the sum of:

-1 + 2 – 3 + 4 – 5 + 6 – 7 + 8 – 9 + 10 – 11 + 12 – 13 + 14 – 15 + 16

Displayed in grid form, the problem in question contained a greater number of values and was asked in a slightly different way, but the takeaway is the same: The GMAT likes to ask questions that seem to require a time-consuming calculation, but can actually be solved relatively quickly through pattern recognition, leading to simpler math.

In this case, each pair of odd-then-even values sums to 1. (-1 + 2), (-3 + 4), etc. will each produce a sum of 1, meaning that the test-taker only need to recognize that pattern, determine the number of pairs* that exist in the sequence (in this case, 8), and multiply the sum of each pair by the number of pairs (1 * 8) to achieve the answer, 8.

The takeaway? When problems look to require extensive calculation, or when you detect that a pattern may be present, look to find a pattern that can make the solution quick and efficient. The GMAT rewards that style of thinking more often than not.

(*Note: be sure in this case to determine whether the sequence does, indeed, contain only distinct pairs; to make the question more difficult, the sequence could end with -17, in which case that value wouldn’t have a complementary positive number, and would have to be subtracted entirely.)

If you’re in the early stages of your GMAT preparation, Veritas Prep offers the Official Guide for GMAT Review, 12th Edition, for just $10. It’s a great way to get started!

One Response

Leave a Reply

Spam protection by WP Captcha-Free