The distance between two settlements located on the river bank is 10 km. The boat travels this distance against

The distance between two settlements located on the river bank is 10 km. The boat travels this distance against the current in 0.25 hours. The boat’s own speed is 60 km / h. How long will it take it to cover this distance downstream?

Data: S (distance between settlements, boat route) = 10 km; t1 (time of movement downstream) = 0.25 h; Vк (own speed of a given boat) = 60 km / h.

1) Current speed: S = (Vк – Vт) * t1, whence Vт = Vк – S / t1 = 60 – 10 / 0.25 = 20 km / h.

2) The time spent by a given boat to move downstream: t2 = S / (Vк + Vт) = 10 / (60 + 20) = 0.125 h (7.5 min).

Answer: The boat will go 10 km downstream in 7.5 minutes.