A person walking across the room with a constant speed of 2m/s, and they run back with a constant speed of 8m/s. What is their average speed for the trip? I know the answer is 3.2m/s but I need help knowing how it's done. Greatly appreciated!
t = d / r
across ... t = d / 2
back ... t = d / 8
total time ... d/2 + d/8 = 5d/8
total distance ... d + d = 2d
average speed ... 2d / (5d/8) = 16d / 5d