SOLUTION: An inlet pipe can fill a tank in 6 minutes. A drain can empty the tank in 18 minutes. If the tank is empty, and both the pipe and drain are open, how long will it take before the t

Question 901579: An inlet pipe can fill a tank in 6 minutes. A drain can empty the tank in 18 minutes. If the tank is empty, and both the pipe and drain are open, how long will it take before the tank overflows?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Filling or draining a tank is 1 job
Filling 6 minutes
so it does 1/6 of the job in 1 minute
draining -18 minutes
so it does 1/18 of the job in 1 minute
If both are open effective rate will be
1/6 - 1/18
2/18
= 1/9
so 1/9 of the job is done in 1 minute
It will take 9 minutes to fill the tank
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