Question

Один насос может откачать за минуту 4 л воды, а второй - 5 л. Сколько воды могут откачать эти насосы за 7 минут при совместной работе? За какое время они могут откачать 81 л воды, работая одновременно.

Answer 1

5+4=9 литров в минуту оба насоса
9*7=63 литра за 7 минут
81:9=9 мин

Answer 2

Problem Analysis

We are given two pumps that can pump water at different rates. Pump 1 can pump 4 liters of water in 1 minute, while Pump 2 can pump 5 liters of water in 1 minute. We need to determine how much water these pumps can pump in 7 minutes when working together, as well as how long it would take for them to pump 81 liters of water when working simultaneously.

Solution

To find out how much water the pumps can pump in 7 minutes when working together, we need to calculate the combined pumping rate of the two pumps.

The combined pumping rate is the sum of the individual pumping rates of the two pumps.

Let's calculate the combined pumping rate:

Pump 1: 4 liters/minute Pump 2: 5 liters/minute

Combined pumping rate = Pump 1 rate + Pump 2 rate = 4 liters/minute + 5 liters/minute = 9 liters/minute

Now, we can calculate the total amount of water pumped in 7 minutes:

Total water pumped = Combined pumping rate * Time

Total water pumped = 9 liters/minute * 7 minutes = 63 liters

Therefore, when working together for 7 minutes, the two pumps can pump 63 liters of water.

To find out how long it would take for the pumps to pump 81 liters of water when working simultaneously, we can use the same formula:

Total water pumped = Combined pumping rate * Time

81 liters = 9 liters/minute * Time

Time = 81 liters / 9 liters/minute = 9 minutes

Therefore, when working together, the two pumps can pump 81 liters of water in 9 minutes.

Answer

- When working together for 7 minutes, the two pumps can pump 63 liters of water. - When working together, the two pumps can pump 81 liters of water in 9 minutes.

Please let me know if there is anything else I can help you with.