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One inlet pipe can fill an empty pool in 6 hours, and a drain can empty the pool in 9 hours. how long will it take the pipe to fill the pool if the drain is left open?

User Derpda
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1 Answer

2 votes
inlet pipe can fill the pool in 6 hours, means: every hour the pool is filled 1/6
a drain can empty the pool in 9 hours, means: every hour the pool is drained 1/9
If the inlet and the drain are both left open, every hour the pool is filled 1/6-1/9=1/18
It will take 18 hours to fill up the pool.
User Joseramonc
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