A driver covers a certain distance by car driving at 60 km/hr and returns back to the starting point riding on a scooter at 15 km/hr. What was the average speed for the whole journey? Select the correct option:
A) 20 km/h
B) 22 km/h
C) 24 km/h
D) 26 km/h
E) 28 km/h
time 1 = d / 60   time 2 = d / 15   total time = d/60 + d/15 = 5d/60 = d/12   average speed = total distance / total time = 2d / (d/12) = 24 km/h   The answer is 24 km/h.
<result>C</result>
A driver covers a certain distance by car driving at 60 km/hr and returns back to the starting point riding on a scooter at 15 km/hr. What was the average speed for the whole journey?