Official Guide Explanation:
Problem Solving #146




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Solution and Metadata

Question: 146
Page: 81
Difficulty: 6 (Moderately Difficult)
Category 1: Word Problems > Sets >
Category 2: Arithmetic > Sets > 2 sets

Explanation: Say the number of passengers is t. Thus, if 20% of the passengers held round - trip tickets and took their cars aboard, c&r = 0.2t . (c stands for those who took their cars aboard, and r for those with round - trip tickets.) If 60% of the passengers with round - trip tickets did not take their cars aboard, that means 40% DID take their cars aboard. Thus, c&r = 0.4r. Since we have two equations where one side is c&r, we can set the other sides equal to each other:

0.2t = 0.4r

r = ((0.2)/(0.4))t = 0.5t

Half of the total passengers held round - trip tickets. Choice (C) is correct.

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