shasadou wrote:

On a certain Monday, Carlos drove to work at an average speed of 50 miles per hour and home from work along exactly the same route at an average speed of 70 miles per hour. Which of the following is closest to his average speed for both trips combined?

A. 58.3 miles per hour

B. 60.0 miles per hour

C. 62.6 miles per hour

D. 65.4 miles per hour

E. It cannot be determined from the information given

To solve the average speed questions, we need to know the total distance and the total time.

Let us assume that the distance from work = D

This will also be the distance from work to home

Hence total distance travelled = 2D

Time in going to work = D/50,

Time in coming back from work = D/70

Hence average speed of both the trips = 2D/ (D/50 + D/70)

= 2*350/12 = 58.33 (Option A)