Question

Теплоход проплывает по течению реки расстояние между двумя городами за 4 часа, по озеру это же расстояние он проплывает за 5 часов. За какое время это же расстояние проплывет плот?

Answer 1

1) 1 : 4 = 1/4 часть проходит теплоход по течению реки за 1 час
2) 1 : 5 = 1/5 часть проходит теплоход по озеру за 1 час
3) 1/4 - 1/5 = 5/20 - 4/20 = 1/20 часть расстояния на которое за час течение сносит плот
4) 1 : 1/20 = 1 * 20 = 20 часов потребуется плоту
Ответ: 20 часов потребуется плоту

Answer 2

Calculation of Speed

To determine the time it takes for a raft to travel the same distance, we need to calculate the speed of the steamboat in both the river and the lake.

Let's assume the distance between the two cities is D.

The speed of the steamboat in the river can be calculated as D/4 (since it takes 4 hours to cover the distance in the river).

The speed of the steamboat in the lake can be calculated as D/5 (since it takes 5 hours to cover the distance in the lake).

Calculation of Time for the Raft

To find the time it takes for the raft to cover the same distance, we need to calculate the speed of the raft.

Let's assume the speed of the raft is R.

Since the distance covered by the steamboat in the river is the same as the distance covered in the lake, we can equate the speeds:

D/4 = D/5 = R

Simplifying the equation, we find:

5D = 4D = 4R

Therefore, the speed of the raft is 4/5 times the speed of the steamboat.

To find the time it takes for the raft to cover the distance, we can use the formula:

Time = Distance / Speed

Substituting the values, we have:

Time = D / (4/5) = 5D / 4

Therefore, the time it takes for the raft to cover the same distance is 5D/4.

Conclusion

In conclusion, the raft will take 5D/4 hours to cover the same distance that the steamboat covers in 4 hours in the river and 5 hours in the lake.

Please note that the specific values for the distance between the two cities and the speed of the steamboat were not provided in the question, so we cannot provide an exact numerical answer. However, the formula and calculation provided above can be used to find the time for any given distance and speed.