GRE Solutions Manual, Problem 5.19

Exam Prep, GRE, Quantitative Reasoning

This page is part of my unofficial solutions manual to the GRE Paper Practice Book (2e), a free resource available on the ETS website. They publish the questions; I explain the answers. If you haven’t worked through the Practice Book, give Section 5 a shot before reading this!

5.19: Percent Comparisons

This problem is best approached in terms of percent change, using the same principles as we’d employ to figure out a percent discount or markup. Following the examples in the Math Review (pp. 11-12), we can write the basic formula for such problems as

GRE 5.19, Eqn. 1

We’re instructed to find the “percent less than” the income tax revenue, so the income tax revenue will be our base (the denominator). The numerator will be the difference between the income tax revenue and the gas tax revenue. Putting that all together, we get:

GRE 5.19, Eqn. 2

The gasoline tax revenue is 28.7% less than the income tax revenue. Of the answer choices, the closest approximation to this figure is 30% (answer C).


Math Review Reference

For more on this topic, see the following sections of the GRE Math Review:

  • 1.7: Percent (pp. 9-12)
  • 4.1: Graphical Methods for Describing Data (pp. 64-65)