Question 731546
A filler pipe can fill a tank in 10 hours, while an outlet pipe can empty the tank in 15 hours.  How long will it take to fill the empty tank with both pipes operating?
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In one hour, the filler adds 1/10 of the tank.
The outlet releases 1/15 of the tank.
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Net gain per hour = 1/10 - 1/15 = 1/30 of the tank
--> 30 hours