Posted by TinaG on .
One pipe can fill a swimming pool in 8 hours.
Another pipe takes 12 hours. How long will it take to fill the pool if both pipes are used simultaneously?

Algebra 
Anonymous,
Pipe A will fill 1/8 of the pool is 1 hour. Pipe B will fill 1/12 of the pool in 1 hour.
So, 1/8 + 1/12 = 5/24
It will take 4.8 hours to fill the pool. 
Algebra 
Andre,
it will fill it in 24 hours, because 1/81/12= 1/24. So it will be 24 hours. We are subtracting, the two because the water is draining out at the same time.