The pool can be filled through two pipes. The first pipe fills the pool in 3 hours

The pool can be filled through two pipes. The first pipe fills the pool in 3 hours, and the second in 6 hours. How many hours will both pipes fill the pool together?

Let’s find out which part of the pool each of the pipes fills in one hour.

In the problem statement, it is said that the first pipe fills the entire pool in 3 hours, and the second in 6 hours, therefore, in one hour, the first pipe can fill 1/3 of the pool, and the second pipe – 1/6 of the pool.

Then if two pipes are open at the same time, then in one hour they will fill 1/3 + 1/6 = 2/6 + 1/6 = 3/6 = 1/2 part of the pool.

Therefore, two pipes can fill the entire pool in 1 / (1/2) = 2 hours.

Answer: in 2 hours.