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## Official Guide Explanation:Data Sufficiency #28

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.

Question: 28
Page: 155
Difficulty: 5 (Moderate)
Category 1: Algebra > Exponents >
Category 2: Arithmetic > Powers and Roots of Numbers > Powers

Explanation: To find the value of ((y)/(x)), you'll need the value of each variable or the ratio between them. Statement (1) is insufficient: it has no information about y. Statement (2) is also insufficient: if x2 = y2, x could equal y, but x could also be -y; for example, if x = 4, x2 = 16, and if y2 = 16, then y could be 4 or -4.

Taken together, the statements are still insufficient. If x = 6, then x2 = 36. If y2 = 36, then y = 6 or y= - 6. Depending on which value of y is correct, the value of ((y)/(x)) could be 1 or -1. Choice (E) is correct.

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