SOLUTION: It takes 10 hours to fill a pool with water, and 20 hours to drain it. If the pool is empty and the drain is open, how long will it take to fill the pool?

Question 231075: It takes 10 hours to fill a pool with water, and 20 hours to drain it. If the pool is empty and the drain is open, how long will it take to fill the pool?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
It takes 10 hours to fill a pool with water, and 20 hours to drain it. If the pool is empty and the drain is open, how long will it take to fill the pool?
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Fill rate : 1/10 job/hr
Drain rate: 1/20 job/hr
Together rate: 1/x job/hr
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Equation:
1/10 - 1/20 = 1/x
Multiply thru by 20x to get:
2x - x = 20
x = 20 (number of hours required to fill the pool)
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Cheers,
Stan H.
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