SOLUTION: A swimming pool holds 54 cubic meters of water. It can be drained at a rate of one cubic meter minute faster than it can be filled. If it takes 9 minutes longer to fill it than to

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Question 1081540: A swimming pool holds 54 cubic meters of water. It can be drained at a rate of one cubic meter minute faster than it can be filled. If it takes 9 minutes longer to fill it than to drain it, find the drainage rate.
Answer by ikleyn(52855) About Me  (Show Source):
You can put this solution on YOUR website!
.
The drainage rate is 3 m^3 per minute.

I solved it mentally.


But if you want to see the equations, here they are. 

Let d = the drainage rate, in m^3/minute.
    f = the filing rate.


Then 

d - f = 1,

54%2Ff - 54%2Fd = 9.


From the first equation, express f = d-1 and substitute it into the second equation. You will get

54%2F%28d-1%29 - 54%2Fd = 9.


Solve it for d.