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## Official Guide Explanation:

Data Sufficiency #8

**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.

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**Solution and Metadata**

**Question****: 8**

Page: 153

Difficulty: **4** (Moderately Easy)

Category 1: Word Problems > Sets >

Category 2: Arithmetic > Sets > 2 sets

**Explanation:** Statement (1) is not sufficient: it doesn't have any information about the schedules of Y and Z. Statement (2) is also insufficient, as it has no information about the schedules of W and Z.

Taken together, the statements are sufficient. Since you have the relevant schedules for W, X, Y, and Z, you can determine that all four have an open period between 10:00 and 11:00 a.m. Choice (C) is correct.

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