Miles drives the same path to and from work. If he averages 50 miles per hour on the way to work and 75 miles per hour on the way from work, what is the average speed of his entire commute?
total distance / total time = average speed
d / 50 = time1
d /75 = time 2
total distance = 2d
2d /(d/50 + d/75) = avg speed
= 2 / (1/50 + 1/75) = 60 m/hr average