Question

Помогите) Расстояние между двумя пунктами, равное 3,6 км, проплыли по течению за 30 минут, а против течения за 40 минут. Определите скорость течения реки. За сколько часов это же расстояние проплывут плоты?

Answer 1

1) 3600 : 30 = 120 м/мин скорость по течению
2) 3600 : 40 = 90 м/мин скорость против течения
3) (120 - 90 ) : 2 = 15 м/мин скорость реки
Плот по течению будет плыть со скоростью течения т.е. 15 м/мин
4) 3600 : 15 = 240 минут = 4 часа проплывет это расстояние плот

Answer 2

Problem Analysis

We are given the following information: - The distance between two points is 3.6 km. - The time taken to travel downstream (with the current) is 30 minutes. - The time taken to travel upstream (against the current) is 40 minutes.

We need to determine the speed of the river's current and the time it would take for rafts to cover the same distance.

Solution

Let's assume the speed of the river's current is x km/h.

To find the speed of the current, we can use the formula: Speed = Distance / Time

1. Downstream speed: - Distance = 3.6 km - Time = 30 minutes = 0.5 hours - Speed = Distance / Time = 3.6 km / 0.5 hours = 7.2 km/h

2. Upstream speed: - Distance = 3.6 km - Time = 40 minutes = 0.67 hours - Speed = Distance / Time = 3.6 km / 0.67 hours ≈ 5.37 km/h

The speed of the current can be calculated as the difference between the downstream and upstream speeds: Speed of current = Downstream speed - Upstream speed

Substituting the values: Speed of current = 7.2 km/h - 5.37 km/h ≈ 1.83 km/h

Therefore, the speed of the river's current is approximately 1.83 km/h.

To find the time it would take for rafts to cover the same distance, we can use the formula: Time = Distance / Speed

Substituting the values: Time = 3.6 km / 1.83 km/h ≈ 1.97 hours

Therefore, it would take approximately 1.97 hours for the rafts to cover the same distance.

Conclusion

The speed of the river's current is approximately 1.83 km/h. The rafts would take approximately 1.97 hours to cover the same distance.

Please note that the calculations are approximate and may vary slightly depending on the exact values used.