Bob drove to the store( a distance fo 10.5) miles at ana average speed of 35 mile per hours. On the way home, he got stuck in traffic, and he only averaged 15 miles per hour along the same route. What was his average speed for the round trip ?

Answer 1

time=distance/speed, so we have

10.5/35 + 10.5/15 = 21/s

Answer 2

21 mph