Sloan the sloth crawls at 100 meters per hour when crawling uphill, 120 meters per hour when crawling across flat ground, and 150 meters per hour when crawling downhill. One day, Sloan crawls across the forest floor from a tree stump to a spring, and then takes the same route in reverse to return to the tree stump. What was Sloan's average speed during the entire round trip?

  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.