Official Guide Explanation:
Problem Solving #7




This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Quantitative Review (2nd 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: 7
Page: 62
Difficulty: 4 (Moderately Easy)
Category 1: Geometry > Lines >

Explanation: Since the diagonal line bisects angle ACD, we know that the two angles it creates are half the measure of the right angle. Since a right angle is 90 degrees, each of the angles are 45 degrees. The two angles formed by the diagonal line must sum to 180 degrees (this is true of any angles that combine to form a straight line), so combine x with one of the 45 degree angles formed by the diagonal:

180 = x + 45

x = 135, choice (E).

Click here for the full list of GMAT Quant Review explanations.


You should follow me on Twitter. While you're at it, take a moment to subscribe to GMAT Hacks via RSS or Email.

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.