A person first walked at a speed of 5 km / h, and then for the same amount of time rode a bicycle at a speed of 15 km / h.

A person first walked at a speed of 5 km / h, and then for the same amount of time rode a bicycle at a speed of 15 km / h. What is the average speed of a person all the way?

1) Vcp = S all / T all
Since the time is the same at all sites, then V av = S1 + S2 / 2T
2) From the formula V = S / T, we express S and substitute it into the average speed formula:
S = V * T
Vcp = (V1T + V2T) / 2T
3) take T out of the bracket
And T is reduced: Vcp = V1 + V2 / 2
4) substitute the values into the formula
Vcp = 5 + 15/2 = 10km / h
Answer: 10km / h