In 2 hours 40 minutes, a motor boat travels a distance of 48 km downstream.

In 2 hours 40 minutes, a motor boat travels a distance of 48 km downstream. How long will it take it to travel back if the current speed is 3 km / h?

These tasks: t1 (duration of boat movement downstream) = 2 hours 40 minutes (8/3 hours); S (distance traveled) = 48 km / h; Vт (current speed) = 3 km / h.

1) The speed of the considered boat along the current: V1 = S / t1 = 48 / (8/3) = 18 km / h.

2) The speed of the boat under consideration against the current: V2 = V1 – 2Vt = 18 – 2 * 3 = 12 km / h.

3) Duration of movement of the boat on the way back: t2 = S / V2 = 48/12 = 4 hours.

Answer: The boat will be able to travel back in 4 hours.