Official Guide Explanation:
Problem Solving #207

 

 

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.

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Solution and Metadata

Question: 207
Page: 182
Difficulty: 6 (Moderately Difficult)
Category 1: Algebra > Linear Equations-One Unk >
Category 2: Word Problems > Rate Problems > other

Explanation: The variable isn't the usual one for a weighted average problem, but it still boils down to the same formula. The total number of days is n + 1, so the formula looks like this:

((50n + 90(1))/(n + 1)) = 55

50n + 90 = 55n + 55

35 = 5n

n = 7, choice (E).

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