Originally Posted by **hoeltgman**

The main problem here is to put the text into equations. So let's do that first.

We'll call:

x= first pipe water

y= second pipe water

z= third pipe water

In order to avoid any discussion with 0 divisions, we suppose that the amount water we get from the pipes is different from 0.

For the pool I suppose that it is empty when the result of an equation is 0. If it's full, it's 1.

In that case we get:

2x+y=1 (1)

2y+z=1 (2)

4/3x+4/3y+az=1 (3)

a is the time in hours we need to fill up the pool with the third pipe.

From now on, it should be easy:

(1) --> y=1-2x

(2) --> z=1-2y

Put into (3):

you will get x=1/4 (you will eventually need to substitute an y with (1).)

this helps us to find y in (2): y=1/2

Put these two results in (3) again and you get a=0. You actually don't need the third pipe anymore