Math
posted by Lilia .
Paul drove from his house to work at an average speed of 40 miles per hour. The drive took him 15 minutes. If the drive home took him 20 minutes and he used the same route in reverse, what was his average speed going home?

Speed = distance / time
20 minutes = 20/60 = 1/3 hr
Speed = 40 miles / (1/3) hr
Speed = 120 mp/h
Hence, his average speed returned home is 120 mile per hour.