Question

Расстояние,равное 3,6 км, проплыли по течению за 30 мин., а против течения за 40 мин. Определите скорость течение реки.За сколько часов это же расстояние проплывут плоты? Если не трудно, то с объяснением напишите.

Answer 1

30 минут = 1/2 часа
40 минут = 2/3 часа
1) 3,6 : 1/2 = 7,2 (км/ч) - по течению реки
2) 3,6 : 2/3 = 5,4 (км/ч) - против течения реки
Составим уравнение:
7,2 - х = 5,4 + х
х + х = 7,2 - 5,4
2х = 1,8
х = 1,8 : 2
х = 0,9 (км/ч) - скорость течения
3) 3,6 : 0,9 = 4 (ч)

Answer 2

Calculation of River Current Speed

To determine the speed of the river current, we can use the formula:

Speed = Distance / Time

Given that the distance traveled downstream is 3.6 km and the time taken is 30 minutes (0.5 hours), we can calculate the speed of the river current:

Speed downstream = 3.6 km / 0.5 hours = 7.2 km/h.

Similarly, for the distance traveled upstream of 3.6 km and the time taken of 40 minutes (0.67 hours), we can calculate the speed of the river current:

Speed upstream = 3.6 km / 0.67 hours = 5.37 km/h.

Explanation of River Current Speed Calculation

When an object moves with the current of a river, its effective speed is increased by the speed of the current. Conversely, when an object moves against the current, its effective speed is decreased by the speed of the current.

In this case, the boat is moving with the current downstream and against the current upstream. The difference in time taken to cover the same distance in both directions is due to the opposing forces of the boat's speed and the river current.

To find the speed of the river current, we can subtract the speed of the boat upstream from the speed of the boat downstream:

Speed of the river current = Speed downstream - Speed upstream = 7.2 km/h - 5.37 km/h = 1.83 km/h.

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

Calculation of Time for Rafts to Cover the Same Distance

To calculate the time it would take for rafts to cover the same distance, we need to know the speed of the rafts. Unfortunately, the speed of the rafts is not provided in the question. Without this information, we cannot determine the time it would take for the rafts to cover the distance.

If you have any additional information or if there is anything else I can assist you with, please let me know!