Official Guide Explanation:
Problem Solving #21




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Solution and Metadata

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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