Brian drove 120 miles at speed of 60 miles per hour. He drove the same distance back home at average speed of 40 miles per hour. What is his average speed?

Average speed = Total distance/Total time.

First drive:

120/60=2 (distance/rate=time)

Second drive:

120/40=3 (distance/rate=time)

Average:

Total time=120+120=240

Total time=3+2=5

Average speed = Total distance/Total time=240/5=48

His average speed was 48 mph.