SOLUTION: one pipe can fill a pool in 10 hours and another drain pipe can empty the pool in 15 hours. if both of the pipes are open, how long will it take to fill the pool?

Question 738512: one pipe can fill a pool in 10 hours and another drain pipe can empty the pool in 15 hours. if both of the pipes are open, how long will it take to fill the pool?
Answer by josgarithmetic(39620) (Show Source): You can put this solution on YOUR website!
The rates are simply added, since this is a uniform rates situation. You have been given the rates in the unit of time per "the job". "The job" is either filling or emptying the pool, and sign is negative or positive depending on emptying or filling.
SUM these rates: . Note that units are job/hour. Note too, the resulting number will be a positive fraction. Again units are job/hour. You may want how many hours per job, so, y....... !

(HINT: Reciprocal)
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