Official Guide Explanation:
Data Sufficiency #142

Background

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Solution and Metadata

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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