Question

Наполнение плавательного бассейна водой может осуществляться одним или двумя насосами. Первый насос, работая в одиночку, может за 7 часов наполнить бассейн, второй за 5 часов. Сколько потребуется времени для наполнения бассейна, если включить оба насоса одновременно

Answer 1

Я всегда решаю так 
              работа              скорость                                          время
1насос        1                      1\7работы в час                            7часов
2насос         1                      1\5 работы в час                              5часов
вместе         1                       (1\7+1\5)=12/35                    1 : 12\35=2часа11\12 часа
по моему так)

Answer 2

Calculation of Time to Fill the Pool with Two Pumps

To calculate the time required to fill the pool when both pumps are turned on simultaneously, we need to consider the rates at which each pump fills the pool individually.

According to the information provided, the first pump can fill the pool in 7 hours when working alone, while the second pump can fill the pool in 5 hours when working alone.

To determine the time it takes to fill the pool when both pumps are turned on simultaneously, we can use the concept of work rates. The work rate of a pump is the reciprocal of the time it takes to complete a task. In this case, the work rate of the first pump is 1/7 of the pool per hour, and the work rate of the second pump is 1/5 of the pool per hour.

When both pumps are turned on simultaneously, their work rates are additive. Therefore, the combined work rate of both pumps is (1/7 + 1/5) of the pool per hour.

To find the time required to fill the pool, we can take the reciprocal of the combined work rate. Let's calculate it:

Combined work rate of both pumps: 1/7 + 1/5 = 12/35 of the pool per hour

Time required to fill the pool: Reciprocal of the combined work rate = 35/12 hours

Therefore, it will take approximately 2.92 hours (or 2 hours and 55 minutes) to fill the pool when both pumps are turned on simultaneously.

Please note that the above calculation assumes that the pumps work at a constant rate and there are no other factors that may affect the filling time of the pool.

Conclusion

When both pumps are turned on simultaneously, it will take approximately 2.92 hours (or 2 hours and 55 minutes) to fill the pool.