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?
Let's give some distances 100 up 100 flat 100 down meters
then return 100 up 100 flat 100 down
time required (distance/rate = time ) 200/100 + 200/120 + 200 / 150 = 5 hr
distance / time = average speed = 600/5 = 120 m/s