Official Guide Explanation:
Data Sufficiency #75

Background

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Solution and Metadata

Question: 75
Page: 158
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Descriptive Statistics > Average
Category 2: Arithmetic > Percents > other
Category 3: Algebra > Linear Equations-Two Unk >

Explanation: Statement (1) is sufficient: if Team A played 25 games, then it played 5 games after the first 20. Since it won 10 of the first 20 games and all of the remaining 5 games, it won a total of 15 games. Statement (2) is also sufficient. The percent of games Team A won is given by ((10 + r)/(20 + r)), where r is the number of remaining games after the first 20. If ((10 + r)/(20 + r)) = 0.6, you can solve for r, then add that number to 10 to find the total number of games Team A won. Choice (D) is correct.

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