A driver covers a certain distance by car driving at 50 km/hr and returns back to the starting point riding on a scooter at 10 km/hr. What was the average speed for the whole journey?  Choose the correct option:
A) 12.5 km/h  B) 14.8 km/h  C) 16.7 km/h  D) 17.5 km/h  E) 18.9 km/h
time 1 = d / 50   time 2 = d / 10   total time = d/50 + d/10 = 3d/25   average speed = total distance / total time = 2d / (3d/25) = 16.7 km/h   The answer is 16.7 km/h.
<result>C</result>
A driver covers a certain distance by car driving at 50 km/hr and returns back to the starting point riding on a scooter at 10 km/hr. What was the average speed for the whole journey?