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## Official Guide Explanation:Problem Solving #12

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: 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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