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## Official Guide Explanation:Problem Solving #D07

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: D07
Page: 21
Difficulty: 6 (Moderately Difficult)
Category 1: Arithmetic > Discrete Probability >

Explanation: The simplest way to look at this is to recognize that each member of the group has an equal chance of being chosen for any of the positions. Since there are 10 members, there is a one - in - ten chance that any member is chosen for any of the three positions.

Thus, there is a (1/10) probability that Harry is chosen to be secretary, and a (1/10) probability that he is chosen to be treasurer. Since it's impossible that he can be chosen to be both, we don't need to worry about that possibility. The probability that he is chosen for one or the other is the sum of the two probabilities:

(1/10) + (1/10) = (2/10) = (1/5), choice (E).

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