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Official Guide Explanation:Data Sufficiency #42

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: 42
Page: 156
Difficulty: 6 (Moderately Difficult)
Category 1: Arithmetic > Percents > other
Category 2: Algebra > Inequalities > other
Category 3: Arithmetic > Ratio and Proportion >

Explanation: Given the equation y > (1.1)x, you need to know the value of x (or possibly a range of x) to determine the value (or the range) of y. Statement (1) is sufficient: if x > 75, then y > (1.1)(75), which is greater than 75. Statement (2) can be rearranged in terms of x, then plugged into the inequality:

y - x = 10

y = 10 + x

(10 + x) > (1.1)x

10 > (0.1)x

100 > x

If x is less than 100, it may or may not be greater than 75, so the statement is insufficient. Choice (A) is correct.

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