The easiest way to do this one is to plug in a number for x.
Let's say that he drove 100 miles, so x = 100.
If he drove 100 miles:
5 miles at 30 mph = 10 minutes
95 miles at 60 mph = 95 minutes
Total = 105 minutes
Now, if he had gone 100 miles at 60 mph, that'd be 100 minutes. So, he was 5 minutes slower, or 5%.
Plug in 100 for x in the answers, and look for the one that is 5%, or answer choice E.
Gmat prep speed question
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Source: Beat The GMAT — Problem Solving |












