Question

On the way to visit her grandmother, Sally drove at an average speed of 85 mph. On the way home (taking the same route) she only averaged 65 mph. If the total round trip took 18 hours, how many hours did it take Sally to drive to her grandmother's? Write your answer as a decimal.​

Answer 1

7.8 hours

Explanation:

We will use the formula:

distance =rate×time

We don't know the distance but it is the same distance going and returning. Two rate×time calculations will both equal that distance from Sally's to Grandma's. See image.