Question

Катер прошел от одной пристани до другой 240 км и вернулся обратно.Найдите среднюю скорость катера на всем пути , если его собственная скорость 18 км\ч , а скорость течения 2 км\ч.

Answer 1

240*2=480(км) - весь путь
18+2=20(км/ч) - скорость по течению
18-2=16(км/ч) - скорость против течения
240:20=12(час) - время в пути по течению
240:16=15(час) - время  в пути против течения
12+15=27(час) - время в пути туда и обратно
480:27=17 7/9(км/ч) - средняя скорость

Answer 2

Calculation of Average Speed

To calculate the average speed of the boat, we need to consider both its own speed and the speed of the current.

Given: - Boat's own speed: 18 km/h - Speed of the current: 2 km/h - Distance traveled from one dock to another: 240 km

To find the average speed, we can use the formula:

Average Speed = Total Distance / Total Time

Since the boat travels from one dock to another and then returns back, the total distance covered is twice the distance between the docks, which is 240 km * 2 = 480 km.

To find the total time, we need to consider the time taken for the boat to travel from one dock to another and the time taken for the return journey.

Let's calculate the time taken for one leg of the journey first:

Time = Distance / Speed

For the boat's own speed of 18 km/h: Time taken for one leg = 240 km / 18 km/h = 13.33 hours

Now, let's calculate the time taken for the return journey, considering the speed of the current:

Time = Distance / (Speed of the boat + Speed of the current)

For the boat's own speed of 18 km/h and the speed of the current of 2 km/h: Time taken for the return journey = 240 km / (18 km/h + 2 km/h) = 12 hours

Now, we can calculate the total time taken for the entire journey:

Total Time = Time taken for one leg + Time taken for the return journey

Total Time = 13.33 hours + 12 hours = 25.33 hours

Finally, we can calculate the average speed:

Average Speed = Total Distance / Total Time

Average Speed = 480 km / 25.33 hours ≈ 18.95 km/h

Therefore, the average speed of the boat for the entire journey, considering its own speed of 18 km/h and the speed of the current of 2 km/h, is approximately 18.95 km/h.