Official Guide Explanation:
Problem Solving #89

 

 

Background

This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Quantitative Review (2nd 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: 89
Page: 73
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Percents > Percent Change
Category 2: Word Problems > Discount >

Explanation: This is a great question to assign values to the unknown quantities. If the length is 5 and the width is 20, the original area is 5(20) = 100. (It's important to pick simple numbers to work with, and ones that can be easily increased by 20%.) When each dimension is increased by 20%, the length becomes (1.2)(5) = 6, and the width becomes (1.2)(20) = 24. Now, the area is 24(6) = 144. The percent increase then, is given by ((increase)/(original)) = ((144 - 100)/100) = (44/100) = 44%, choice (E).

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