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Official Guide Explanation:Data Sufficiency #55

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: 55
Page: 157
Difficulty: 6 (Moderately Difficult)
Category 1: Word Problems > Rate Problems > Speed
Category 2: Arithmetic > Fractions >

Explanation: To find the time the machine finished filling the order, you need to know what time it started, and how it took to fill the order. Statement (1) is insufficient: there's no indication of how long it took to fill the order.

Statement (2) is sufficient: it indicates that (5/6) - (1/2) = (1/3) of the order could be completed in 40 minutes, which means that the whole order took 40(3) = 120 minutes. Since it was half finished at 10:30 and filling half the order took (120/2) = 60 minutes, it must have started at 9:30, which means it finished at 12:30. Choice (B) is correct.

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