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## Official Guide Explanation:Data Sufficiency #59

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: 59
Page: 157
Difficulty: 6 (Moderately Difficult)
Category 1: Word Problems > Rate Problems > Speed
Category 2: Geometry > Circles > other

Explanation: Given the number of rotations is equal to the length (100 meters) divided by the length per rotation. In other words, we need the length per rotation to solve. Statement (1) is sufficient: the length per rotation is the circumference of the wheel, and with the diameter, you can find the radius, and with the radius you can find the circumference. Statement (2) is not sufficient: we're looking for the length per rotation, not the time per rotation. Choice (A) is correct.

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