<PRE><B>Question 509222</B>
Officials begin to release water from a full man-made lake at a rate that would empty the lake in 18 weeks,but a river that can fill the lake in 25 weeks is replenishing the lake at the same time. How long does it take to empty the lake?
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Empty rate = 1/18 job/week
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Fill rate = 1/25 job/week
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Together rate: 1/x
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Equation:
rate - rate = together rate
1/18 - 1/25 = 1/x
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Multiply thru by 18*25x
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25x - 18x = 18*25
7x = 18*25
x = 64.29 weeks (time required to empty)
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Cheers,
Stan H.
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