Official Guide Explanation:
Problem Solving #12

Background

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Solution and Metadata

Question: 12
Page: 154
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Discrete Probability >
Category 2: Arithmetic > Properties of Integers > Other

Explanation: Probability is the number of desired outcomes divided by the number of possible outcomes. The number of desired outcomes is 100: that's how many three - digit numbers there are with a hundreds digit of 2. The number of possible outcomes is 250: that's the number of digits between 101 and 350, inclusive. Remember, if both endpoints (101 and 350) are including, simply subtracting the numbers will give you an answer than is too small by 1. Finally, the probability is (100/250) = (10/25) = (2/5), choice (A).

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