### Bookshelf

 Total GMAT Math Jeff's complete Quant guide, on sale now!
 Total GMAT Verbal Everything you need to ace GMAT Verbal!
 New: GMAT 111 Improve every aspect of your GMAT prep!

Guides To the Official Guide
(Updated for new editions!)

1,800 Practice Quant Questions

GMAT Question of the Day

GMAT Official Guide
OG Math | OG Verbal

Beginner's Guide to the GMAT

GMAT Hacks Affiliate Program

### Resources

MBA.com
GMAC Official Site
Free GMATPrep Practice Tests

Stacy Blackman Consulting
Book | Essay Guides

GRE HQ
Total GRE Math

Ultimate SAT Verbal

## 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.

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: 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).

 You should follow me on Twitter. While you're at it, take a moment to subscribe to GMAT Hacks via RSS or Email.

 Total GMAT Math The comprehensive guide to the GMAT Quant section. It's "far and away the best study material available," including over 300 realistic practice questions and more than 500 exercises! Click to read more.