SOLUTION: Filling a tank. A water tank has an inlet pip and a drain pipe. a full tank can be emptied in 30 minutes if the drain is opened and as empty tank can be filled I 45 minutes with

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Question 58756: Filling a tank. A water tank has an inlet pip and a drain pipe. a full tank can be emptied in 30 minutes if the drain is opened and as empty tank can be filled I 45 minutes with the inlet opened. If both pipes are accidentally opened when the tank is full, then how long will it take to empty the tank?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Filling a tank. A water tank has an inlet pip and a drain pipe. a full tank can be emptied in 30 minutes if the drain is opened and as empty tank can be filled I 45 minutes with the inlet opened. If both pipes are accidentally opened when the tank is full, then how long will it take to empty the tank?
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Drain Pipe DATA:
Time to empty = (1/2) hr/job ; Rate = 2 job/hr
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Inlet pipe DATA:
Time to fill = (3/4) hr/job ; Rate = (4/3) job/hr
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Working together DATA:
Rate = (4/3) - 2 = -1/3 job/hr
The tank will be emptied at (1/3) per hour.
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EQUATION:
Let "x" be the number of hours to empty the tank.
x(-1/3)=-1 (-1 means 1 empty tank)
x=3 (3 hours to empty the tank)
Cheers,
Stan H.