A tank fills in 6 hours with two pipes. One pipe alone fills it in 10 hours. How many hours will the other pipe alone take?

A tank fills in 6 hours with two pipes. One pipe alone fills it in 10 hours. How many hours will the other pipe alone take?

Explanation

Combined rate = 1/6; first pipe rate = 1/10.

Second pipe rate = 1/6 - 1/10 = 1/15.

So, the second pipe alone fills in 15 hours.