A sportsman on a kayak, moving along the river from A and B, spent 10 minutes, and on the way back, 15 minutes.

A sportsman on a kayak, moving along the river from A and B, spent 10 minutes, and on the way back, 15 minutes. What is the average speed of an athlete if the distance between A and B is 7.5 km?

tav = 10 min = 600 s.

tva = 15 min = 900 s.

Sav = 7.5 km = 7500 m.

Vav -?

To find the average speed of an athlete’s movement Vav, it is necessary to divide the entire path S traveled by him by the entire time of movement t: Vav = S / t.

The entire path S traveled will be the distance between A and B multiplied by 2, since he swam in one direction and the other: S = 2 * Sа.

The time of movement t is found by the formula: t = tav + tva, where tav is the time of movement from point A to B, tva is the time of movement from B to A.

Vav = 2 * 7500 m / (600 s + 900 s) = 10 m / s.

Answer: the average speed of an athlete’s movement is Vav = 10 m / s.