Official Guide Explanation:
Data Sufficiency #3




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Solution and Metadata

Question: 3
Page: 273
Difficulty: 3 (Very Easy)
Category 1: Arithmetic > Discrete Probability >

Explanation: To know the probability that a boy will be selected, you need to know the percentage (or fraction) of students in the class who are boys. Statement (1) gives that information, so it is sufficient. Statement (2) tells you how students are girls, which is not useful unless you know the total number of students (which would allow you to deduce the fraction of students who are girls) or the number of boys (which would let you do the same thing). (2) is insufficient, so the correct answer is (A).

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