Question

Через одну трубу бассейн заполняется за 8 чесов,а через другую опорожняется за 7 часов.За какое время наполнится бассейн,если открыть обе трубы вместе?

Answer 1

открыто две трубы а не одна !
значит нужно 8-7=1
за 1 час

Answer 2

Problem Analysis

We are given two pipes, one that fills a pool in 8 hours and another that empties the pool in 7 hours. We need to determine how long it will take to fill the pool if both pipes are opened simultaneously.

Solution

To solve this problem, we can use the concept of rates. Let's assume that the pool has a capacity of 1 unit (this could be any unit of measurement, such as liters or gallons).

The pipe that fills the pool can fill 1/8 of the pool's capacity per hour, while the pipe that empties the pool can empty 1/7 of the pool's capacity per hour.

When both pipes are opened simultaneously, the net rate of filling the pool is the difference between the filling rate and the emptying rate. Therefore, the net rate is (1/8 - 1/7) of the pool's capacity per hour.

To find the time it takes to fill the pool, we can divide the pool's capacity by the net rate of filling. In this case, the pool's capacity is 1 unit.

Let's calculate the time it takes to fill the pool:

Net rate of filling = (1/8 - 1/7) = 7/56 - 8/56 = -1/56 of the pool's capacity per hour

Since the net rate is negative, it means that the pool is being emptied instead of filled. This suggests that the pool cannot be filled when both pipes are opened simultaneously.

Therefore, the pool will never be filled if both pipes are opened together.

Conclusion

If we open both pipes simultaneously, the pool will not be filled. The net rate of filling is negative, indicating that the pool is being emptied rather than filled.