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## Official Guide Explanation:Problem Solving #132

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: 132
Page: 171
Difficulty: 4 (Moderately Easy)
Category 1: Algebra > Linear Equations-One Unk >
Category 2: Word Problems > Mixture Problems >
Category 3: Arithmetic > Descriptive Statistics > Average

Explanation: This is a classic weighted average problem. As usual, remember that the actual numbers don't matter: it's the difference between them that counts. So, instead of working with an average of \$400 and a first - six - day revenue of \$360, subtract \$360 from everything, leaving an average of \$40 and a first - six - day revenue of \$0. Then, the equation looks like this: ((6(0) + 4(x))/10) = 40. Then: 4x = 400, and x = 100. Since we started by subtracting \$360 from everything, we have to add that back, giving us 100 + 360 = 460, choice (D).

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