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## Official Guide Explanation:Data Sufficiency #142

Background

This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Review (12th 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: 142
Page: 285
Difficulty: 5 (Moderate)
Category 1: Word Problems > Other >
Category 2: Arithmetic > Percents > other

Explanation: Statement (1) is insufficient. We're told what percent of her sales Jean earns as a commission, but to answer the question, we would also need to know her total sales.

Statement (2) is also insufficient. Since we're talking about 6 - month periods, an average of \$10,000 per month higher means that, in the second half of 1988, she sold \$60,000 more than in the first half. Still, this doesn't tell us anything specific about her commission.

Taken together, the statements are still insufficient. Combined, we know that Jean made 5% on \$60,000 less than what she sold in the second half of the year. However, we don't know what that amount is. We need to multiply 5% by some number for sales, and we don't have that number. Choice (E) is correct.

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