Answer:
37.5 mi/h
Step-by-step explanation:
time = distance / speed
On the trip 'going', the time was (150 mi)/(50 mi/h) = 3 h.
On the return trip, the time was (150 mi)/(30 mi/h) = 5 h.
__
speed = distance / time
The average speed for the whole trip was ...
speed = (150 mi +150 mi)/(3 h +5 h) = (300 mi)/(8 h) = 37.5 mi/h
His average rate of speed was 37.5 miles per hour.
