Question

Susan drove at an average speed of 30 miles per hour for the first 30 miles of a trip and then at an average speed of 60 miles per hour for the remaining 30 miles of the trip. If she made no stops during the trip, what was Susan's average speed, in miles per hour, for the entire trip?a. 35

b. 40
c. 45
d. 50
e. 55

Answer 1

Answer: option B is the correct answer.

Explanation:

Susan drove at an average speed of 30 miles per hour for the first 30 miles of a trip.

Time = distance/speed

This means that time spent by Susan in travelling the first 30 miles would be

Time = 30/30 = 1 hour

He travelled at an average speed of 60 miles per hour for the remaining 30 miles of the trip.

Time = 30/60 = 0.5 hours

Total distance travelled is 30 + 30 = 60 miles.

Total time spent = 1 + 0.5 = 1.5 hours

Speed = distance/time

Average speed = 60/1.5 = 40 miles per hour.