SOLUTION: if it takes 10 hours to fill a pool and 20 hours to drain it, how long will it take to fill it if the drain is open?

Question 276432: if it takes 10 hours to fill a pool and 20 hours to drain it, how long will it take to fill it if the drain is open?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
if it takes 10 hours to fill a pool and 20 hours to drain it, how long will it take to fill it if the drain is open?
It fills 1/10th. of the pool in one hour
It drains 1/20th of the pool in 1 hour.
In an hour actually the increase is 1/10-1/20
1/20
with the drain open 1/20th of the pool is filled in one hour.
so to fill the pool it will take 20 hours

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