<PRE><B>Question 281716</B>
 A swimming pool can be filled in 12 hours and drained in 20 hours. If the pool is empty and the drain is open, how long will it take to fill the pool?
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Filling rate: 1/12 job/hr
Drain rate::: 1/20 job/hr
Together rate 1/x job/hr
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Equation:
rate - rate = together rate
1/12 - 1/20 = 1/x
Multiply thru by 60x to get:
5x - 3x = 60
2x = 60
x = 30 hrs (time to fill the pool with both pipes open)
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Cheers,
Stan H.</PRE>