SOLUTION: Please help... A swimming pool holds 540,000 liters of water. The pool has two drainage pipes. When the pool is completely full, the first pipe alone can empty in 150 minutes and

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Question 189865: Please help...
A swimming pool holds 540,000 liters of water. The pool has two drainage pipes. When the pool is completely full, the first pipe alone can empty in 150 minutes and the second pipe alone can empty in 225 minutes. Then both pipes are draining together, how long does it take them to empty the pool? _______minutes.
Found 2 solutions by ptaylor, josmiceli:
Answer by ptaylor(2198) (Show Source):
You can put this solution on YOUR website!
Let x=amount of time it takes both pipes draining together to empty the pool
First pipe empties at the rate of 540,000/150=3600 liters/min
Second pipe empties at the rate of 540,000/225=2400 liters/min
Together, both pipes empties at the rate of 3600+2400=6000 liters/min, so our equation to solve is:
6000*x=540000
x=90 min------------------ans
CK
90*3600+90*2400=540000
324000+216000=540000
540000=540000

Hope this helps---ptaylor

Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
This is a problem adding rates to get a combined rate
You can say that drainage is expressed in pools/minute
For instance, 1 pool/30 sec would be 2 pools/min drained
For this problem in words:
(1st pipe drainage rate) + (2nd pipe drainage rate) =
(both pipes together drainage rate)
Let = the time to drain the pool with both pipes open
Given:

Multiply both sides by

Multiply both sides by

With both pipes are draining together, it takes 90 min to empty the pool
How many liters of water are in the pool
doesn't matter in this problem