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## Official Guide Explanation:Problem Solving #21

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: 21
Page: 155
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Ratio and Proportion >
Category 2: Word Problems > Rate Problems > Combined Rate

Explanation: If six machines can produce 270 bottles per minute, each machine's rate per minute is (270/6). Don't calculate just yet: since that isn't the answer to the question, perhaps a future step will allow some sort of simplification instead. Ten machines working for four minutes are able to do 40 (10 * 4) times the work of one machine in one minute, so the answer is 40((270/6)). To simplify, divide 40 and 6 by 2, which leaves you with 20((270/3)) = 20(90) = 1800, choice (B).

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