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## Official Guide Explanation:

Data Sufficiency #98

**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****: 98**

Page: 160

Difficulty: **5** (Moderate)

Category 1: Arithmetic > Real Numbers >

**Explanation:** Statement (1) is insufficient. If yz < 0, then z is less than zero only if y is greater than zero. (The product of two numbers is negative only when exactly one of the numbers is negative.) If xy > 0, y is only greater than zero when x is greater than zero, so z is only less than zero when x is greater than 0. Statement (2) is insufficient, as it contains nothing about z.

Taken together, the statements are sufficient. (1) establishes that if x is greater than 0, z is less than 0. (2) tells you that x is, indeed, greater than zero. Choice (C) is correct.

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