The bike traveled 20 km. with a speed of 10 km per hour, and the next 25 in 1 hour.

The bike traveled 20 km. with a speed of 10 km per hour, and the next 25 in 1 hour. Find its average speed for the entire journey.

S1 = 20 km.

V1 = 10 km / h.

S2 = 25 km.

t2 = 1 h.

Vav -?

To find the average speed of a cyclist’s movement Vav, it is necessary to divide the entire path S passed by him by the time it passes: Vav = S / t.

Cyclist S’s path will be the sum: S = S1 + S2.

S = 20 km + 25 km = 45 km.

The travel time of the entire path is expressed by the sum: t = t1 + t2, where t1 is the time of movement on the first part of the path, t2 is the time of movement on the second part of the path.

With uniform movement, the movement time t1 is determined by the ratio of the distance traveled S1 to the speed of movement V1: t1 = S1 / V1.

t1 = 20 km / 10 km / h = 2 h.

t = 2 h + 1 h = 3 h.

Vav = 45 km / 3 h = 15 km / h.

Answer: the average speed of a cyclist along the entire path was Vav = 15 km / h.