Average Speed

Question

An automobile traveled 7 hours at an average speed of 50 miles per hour. It averaged only 40 miles per hour on the return trip. The average speed per hour, to the nearest mile, for the round trip was

a) 46 miles per hour

b) 44 miles per hour

c) 43 miles per hour 

D) 47 miles per hour

Answer 1

speed * time = distance

50*7=350

distance is 350

on way back:

speed * time = distance
40*time=350

time=350/40 = 8.75 or 8 hrs and 45 mins

Total:   add time and add distance

speed * time = distance
speed * 15.75 = 700 miles

speed = 700/15.75 = 44.44  (b)