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Official Guide Explanation:Problem Solving #94

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.

Question: 94
Page: 165
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Percents > other
Category 2: Word Problems > Mixture Problems >

Explanation: This is an excellent question to assign a value to the unknown quantity. Say that there are 100 registered voters. That means there are 60 Democrats and 40 Republicans. If 75% of the D's voted for Candidate A, that's 75%(60) = 45. If 20% of the R'd voted for Candidate A, that's 20%(40) = 8. The total number, then, is 45 + 8 = 53. Since the question is looking for a percent, we have to figure out what percent 53 is of the original number; that's what makes 100 such good number to start with: 53 is 53%, choice (B).

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