Two pipes, A and B, can fill a tank individually in 60 minutes and 75 minutes respectively. There is a third pipe located at the bottom of the tank that drains it. If all three pipes are opened at the same time, the tank fills up in 50 minutes. How long will it take for the third pipe alone to empty the tank?

Explanation

The combined filling rate of pipes A and B per minute is 1/60 + 1/75. When all three pipes operate together, the net filling rate is 1/50. The third pipe's emptying rate per minute is the difference: 1/50 - (1/60 + 1/75) = -1/100. The negative sign indicates the pipe empties the tank, so it will take 100 minutes to empty it completely.