A car travels up a hill at a constant speed of 35 km/h and returns down the hill at a constant speed of 66 km/h. How to calculate the average speed for the round trip ?
Distance going up hill
Distance going down hill
Since the distances are equal
Suppose that it was a really long hill that took
In this case it would take
The total time taken would be
the total distance covered would be
the average speed would be
Notice that the proportions remain the same no matter what amount of time you assume it would take to go up the hill.