Maths
posted by 10M1 .
A boy cycled from his home to a friend's house 24km away at an average speed of 16km/h. Finding his friend absent, he returned home immediatly at an average speed of 12km/h. Find the average speed
I know how to find the average speed, just that I need to know how to find out the total distance
Please help me and show working out on how to find the total distance

The boys are 24 km apart and one of them makes a round trip back and forth.
The total distance travelled is 48 km.
Use that and the total elapsed time for the average speed.