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 10 km/hr. What was the average speed for the whole journey?
Pick one:
A) 14.2 km/h B) 17.1 km/h C) 19.3 km/h D) 21.7 km/h E) 23.5 km/h
time 1 = d / 60   time 2 = d / 10   total time = d/60 + d/10 = 7d/60   average speed = total distance / total time = 2d / (7d/60) = 17.1 km/h   The answer is 17.1 km/h.
<result>B</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 10 km/hr. What was the average speed for the whole journey?