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## Official Guide Explanation:

Problem Solving #D09

**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****: D09**

Page: 21

Difficulty: **6** (Moderately Difficult)

Category 1: Arithmetic > Descriptive Statistics > Average

Category 2: Arithmetic > Descriptive Statistics > Standard Deviation

Category 3: Arithmetic > Descriptive Statistics > other

**Explanation:** Consider each of the three measures. If 5 is added to each term, the mean increases by 5. The same happens to the median--whatever the middle number is, it increases by 5. The standard deviation, however, doesn't change. The SD depends on the difference between terms. If every term increases by 5, the difference between the terms doesn't change, so the SD stays the same. Choice (D) is correct.

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