SOLUTION: A tank can be filled by one pipe in four hours and by a second pipe in six hours;and when it is full,the tank can be drained by a third pipe in three hours.If the tank is empty and

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Question 244863: A tank can be filled by one pipe in four hours and by a second pipe in six hours;and when it is full,the tank can be drained by a third pipe in three hours.If the tank is empty and all three pipes are open,in how many hours will the tank be filled?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A tank can be filled by one pipe in four hours and by a second pipe in six hours;and when it is full,the tank can be drained by a third pipe in three hours.
If the tank is empty and all three pipes are open,in how many hours will the tank be filled?
:
Just like a "shared work problem, except the drain fraction is subtracted
:
Let t = time to fill with all pipes open
:
Let the completed job (a full pool) = 1
:
t%2F4 + t%2F6 - t%2F3 = 1
Multiply by 12 to clear the fractions
3t + 2t - 4t = 12
t = 12 hrs to fill the pool
:
:
Check solution on a calc
12/4 + 12/6 - 12/3 =
3 + 2 - 4 = 1