Question 149620
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