Question

Расстояние от пункта A до пункта B моторная лодка, плывя по течению реки, преодолевает за 2,5 ч, а против течения - за 3 ч. Скорость моторной лодки по течению реки равна 20,4 км/ч. Найдите скорость течения.

Answer 1

Vтеч. = (Vпо теч. – Vпр. теч.) :2

1)20,4*2,5=51(км)-расстояние,которое проходит лодка.

2)51:3=17(км/ч)-скорость против течения.

3)(20,4-17):2=3,4:2=1,7(км/ч)-скорость течения.

Answer 2

Calculation of the River Current Speed

To find the speed of the river current, we can use the information provided in the question. Let's denote the speed of the river current as v.

According to the question, the motorboat takes 2.5 hours to travel from point A to point B when moving with the current, and it takes 3 hours to travel from point B to point A when moving against the current. The speed of the motorboat when moving with the current is given as 20.4 km/h.

We can use the formula: distance = speed × time to calculate the distance traveled by the motorboat in each case.

When moving with the current: distance = speed × time distance = 20.4 km/h × 2.5 hours distance = 51 km

When moving against the current: distance = speed × time distance = 20.4 km/h × 3 hours distance = 61.2 km

The distance traveled by the motorboat when moving with the current is 51 km, and when moving against the current is 61.2 km.

Calculation of the River Current Speed

To find the speed of the river current, we can use the formula: speed of the current = (distance against the current - distance with the current) / (time against the current + time with the current).

Substituting the values we calculated earlier: speed of the current = (61.2 km - 51 km) / (3 hours + 2.5 hours) speed of the current = 10.2 km / 5.5 hours speed of the current ≈ 1.8545 km/h

Therefore, the speed of the river current is approximately 1.8545 km/h.