Official Guide Explanation:
Problem Solving #80

 

 

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.

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Solution and Metadata

Question: 80
Page: 163
Difficulty: 5 (Moderate)
Category 1: Word Problems > Work Problems > 2 inputs
Category 2: Arithmetic > Ratio and Proportion >

Explanation: First, find the rate of each machine. A operates at 120 bolts per 40 seconds, or ((120b)/(40s)) = 3((b)/(s)). B operates at 100 bolts per 20 seconds, or ((100b)/(20s)) = 5((b)/(s)). Working together, their cumulative rate is 8((b)/(s)), so they will produce 200 bolts in (200/8) = 25 seconds, choice (B).

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