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## Official Guide Explanation:

Problem Solving #81

**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.

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**Solution and Metadata**

**Question****: 81**

Page: 163

Difficulty: **5** (Moderate)

Category 1: Algebra > Functions > Sequences

Category 2: Word Problems > Data Interpretation >

**Explanation:** To summarize the question, 10 was multiplied by some number, which resulted in a value of x. x was multiplied by the same number, which resulted in 14.4. We can represent that in algebraic form:

10n = x

xn = 14.4

Substitute the first equation into the second:

(10n)n = 14.4

10n^{2} = 14.4

n^{2} = 1.44

n = 1.2

Thus, since x = 10n, x = 10(1.2) = 12, choice (A).

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