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Official Guide Explanation:Problem Solving #D14

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: D14
Page: 22
Difficulty: 7 (Very Difficult)
Category 1: Arithmetic > Sets > 2 sets
Category 2: Word Problems > Sets >

Explanation: This question is very similar to \#6 in the diagnostic. We can use the overlapping sets formula to handle it:

T = G1+ G2 - B + N

84 = 35 + G2 - 11 + N

We know that the number who volunteered to bring refreshments is 1.5x as many as those who volunteered to do neither, so G2 = 1.5N:

84 = 35+ 1.5N - 11+ N

84 - 35 + 11 = 2.5N

60 = 2.5N

N = 24

We're looking for G2, which is 1.5N = 1.5(24) = 36, choice (B).

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