Official Guide Explanation:
Problem Solving #183




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Solution and Metadata

Question: 183
Page: 178
Difficulty: 5 (Moderate)
Category 1: Word Problems > Rate Problems > Speed
Category 2: Arithmetic > Percents > Percent Change

Explanation: The most straightforward way to find the answer to this question is to start by finding car X's rate. r = ((d)/(t)) = (80/2) = 40. 50% faster than 40 miles per hour is 40 + (0.5)(40) = 40 + 20 = 60, so car Y traveled at 60 miles per hour. Now solve for car Y's time:

60 = (80/(t))

60t = 80

t = (80/60)

t = 1(1/3), choice (C).

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