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## Official Guide Explanation:

Problem Solving #79

**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.

Click here for an example of the PDF booklets. Click here to purchase a PDF copy.

**Solution and Metadata**

**Question****: 79**

Page: 163

Difficulty: **5** (Moderate)

Category 1: Arithmetic > Decimals >

Category 2: Algebra > Simplifying Algebraic Expressions >

**Explanation:** Given all of these decimals, try to get rid of as many as possible. To change 0.0036 to 36 requires multiplying by 10,000, so multiply the top and bottom by that amount:

(((0.0036)(2.8))/((0.04)(0.1)(0.003))) * ((10,000)/(10,000))

= ((36(2.8))/((0.04)(1)(3)))

To change 0.04 to 4 requires multiplying by 100, so go through the process again:

((36(2.8))/((0.04)(3))) * (100/100)

= ((36(280))/(4(3)))

= ((36(280))/12) = 3(280) = 840, choice (A).

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