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Question 149620: It takes 4 minutes for the faucet to fill a sink. It takes 3 minutes for the drain to empty the sink. The sink is full, if the drain is open and the faucet turned on at the same time, how long does it take to empty the sink?
Answer by ptaylor(2198)   (Show Source):
You can put this solution on YOUR website! Let x=amount of time it takes to empty the sink with both the faucet and the drain turned on
Faucet fills the sink at the rate of 1/4 sink per min
Drain empties the sink at the rate of 1/3 sink per min
With both the faucet and drain turned on, the sink empties at the rate of
1/3-1/4=4/12-3/12 =1/12 sink per min
So, our equation to solve is:
(1/12)*x=1 (1 sink emptied, that is) multiply each side by 12
x=12 min-------------------------amount of time it takes to empty the sink with both the faucet and the drain turned on
Hope this helps---ptaylor
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