SOLUTION: If a pipe takes 8hours to fill a tank..... And another pipe takes 4 hours to empty the tank.... When both of the pipes are on....how much time will it take to fill the tank????.

Question 774651: If a pipe takes 8hours to fill a tank.....
And another pipe takes 4 hours to empty the tank....
When both of the pipes are on....how much time will it take to fill the tank????..
Answer by josgarithmetic(39620) (Show Source): You can put this solution on YOUR website!
The rates are additive when both pipes are fully open at the same time.
Filling pipe, tank per hour
Emptying pipe, tank per hour

Combined Rate, tank per hour. Notice very carefully that rate of filling is smaller than the rate of emptying. YOU CANNOT FILL THIS TANK WHEN BOTH PIPES ARE OPEN!!

Simplify to tank/hour.
This tank will never fill when both pipes are open all the way.
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