SOLUTION: One pump can drain a pool in 12 minutes. When a second pump is also used, the pool only takes 6 minutes to drain. How long would it take the second pump to drain the pool if it w

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: One pump can drain a pool in 12 minutes. When a second pump is also used, the pool only takes 6 minutes to drain. How long would it take the second pump to drain the pool if it w      Log On


   

Question 127887: One pump can drain a pool in 12 minutes. When a second pump is also used, the pool only takes 6 minutes to drain. How long would it take the second pump to drain the pool if it were the only pump in use?
This is what I tried so far: 1/12 + 1/6 = 1/x 12x/1 x 1/12=1x 12x/1 x 1/6=2x
1x + 2x = 12
3x = 12
x = 4
Answer by Ganesha(13) About Me  (Show Source):
You can put this solution on YOUR website!
The time the first pump alone takes to drain the pool = 12 minutes.
Then in one minute the fraction of draining done by it =1/12 of the pool.
Let the second pump take x minutes.
Then per minute capacity of draining by the second pump = 1/x of the pool.
Therefore, the joint capacity of the two pumps in one minute = 1/12 + 1/x.
But given that the two pumps drain jointly in 6 minutes ,in one minute they drain 1/6 of the pool.Therefore.
1/12 + 1/x = 1/6.=>
1/x = 1/6 - 1/12 = (2-1)/12 = 1/12
1/x = 1/12=>
x = 12 minutes .
Therefore the second pump alone takes 12 minutes to drain the pool.