A motorist makes a trip of 180 miles. For the first 90 miles she drives at a constant speed of 30 mph. At what constant speed must she drive the remaining distance if her average speed for the
Total trip is to be 40 mph?
A) 55 mph
B) 60 mph
C) 52.5 mph
D) 45 mph
E) 50 mph

Question

Quizplus · Accepted Answer

To have an average speed of 40 mph over 180 miles, the total trip time must be 4.5 hours (180 miles / 40 mph). The first 90 miles at 30 mph takes 3 hours. Therefore, the remaining 90 miles must be covered in 1.5 hours, requiring a speed of 60 mph (90 miles / 1.5 hours).

A Motorist Makes a Trip of 180 Miles