Official Guide Explanation:
Problem Solving #D12

Background

This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Review (12th ed.). Click the links on the question number, difficulty level, and categories to find explanations for other problems.

These are the same explanations that are featured in my "Guides to the Official Guide" PDF booklets. However, because of the limitations of HTML and cross-browser compatibility, some mathematical concepts, such as fractions and roots, do not display as clearly online.

Click here for an example of the PDF booklets. Click here to purchase a PDF copy.

Solution and Metadata

Question: D12
Page: 22
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Percents > other
Category 2: Algebra > Linear Equations-Two Unk >

Explanation: The question gives us two equations. First:

y = (1/2)((1/2))(x)

Second:

((y)/100)(x) = 100 ("y percent" is the same as ((y)/100))

Simplifying them:

y = (1/4)x

xy = 10,000

Substitute the first into the second:

x((1/4)x) = 10,000

x² = 40,000

x = 200, choice (C).

Click here for the full list of GMAT OG12 explanations.

Total GMAT Math The comprehensive guide to the GMAT Quant section. It's "far and away the best study material available," including over 300 realistic practice questions and more than 500 exercises! Click to read more.