The first pipe can fill the tank in 10 minutes, the second pipe can fill

The first pipe can fill the tank in 10 minutes, the second pipe can fill the tank in 15 minutes. How many minutes will it take to fill the tank if both pipes are open?

Through the first pipe, you can fill the tank in 10 minutes, which means that 1/10 of the tank is filled from the first pipe in one minute.
1) 1: 10 = 1/10 (part) of the tank is filled in 1 min. through the first pipe.

Through the second pipe, you can fill the tank in 15 minutes, which means that 1/15 of the tank is filled from the second pipe in one minute.
2) 1: 15 = 1/15 (part) of the tank is filled in 1 minute. through the second pipe.

This means that two pipes together fill 1/6 of the tank in 1 minute.
3) (1/10) + (1/15) = (1 * 15) / (10 * 15) + (1 * 10) / (15 * 10) = 15/150 + 10/150 = (15 + 10 ) / 150 = 25/150 = 1/6 (part)

Two pipes fill 1/6 of the tank in a minute, which means they will fill the entire tank in 6 minutes.
4) 1: (1/6) = 1 * (1/6) = 1 * (6/1) = 6 (min.) Two pipes will fill the tank.

Answer: in 6 minutes.