Through the first pipe, you can fill the tank in 4 minutes, through the second – in 12 minutes.

Through the first pipe, you can fill the tank in 4 minutes, through the second – in 12 minutes. How many minutes can it take to fill a tank through two pipes?

To solve this problem by actions, you first need to write down the capacity of the tank as an integer, which is 1.

1) Find the speed of filling the tank through each pipe.

To do this, we divide the capacity of the tank by the time of filling through each pipe.

We get:

1/4 = 1/4 of the tank per minute (1 pipe fills).

1/12 = 1/12 of the tank per minute (2 pipe fills).

2) Find the speed of filling the tank through 2 pipes.

To do this, we summarize the obtained values.

1/4 + 1/12 = 3/12 + 1/12 = 4/12 = 1/3 tank per minute.

3) The filling time will be:

1 / 1/3 = 1 * 3/1 = 3 minutes.

Answer: 3 minutes.