Answer:
120 m/h
Step-by-step explanation:
The time taken to travel a distance d uphill will be ...
time = distance/speed
time = d/100
On the return trip, the same distance will be downhill, so the time will be ...
time = d/150
The average speed on hills is then ...
speed = distance/time = (2d)/(d/100 +d/150) = 2(100)(150)/(100 +150)
speed = 120 . . . . m/h
This is the same as the speed on flat ground. So, the average speed on flat ground is the same as the average speed on hills. That will be Sloan's average speed over any terrain.
Sloan's average speed was 120 m/h.