One pipe fills a tank 9 hours faster than another, and together they fill it in 6 hours. When a third pipe, which empties the tank, is also opened, the three fill the empty tank in 9 hours. How long does the third pipe take to empty the full tank?

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Accepted Answer

18 h. 1/x+1/x+9=1/6 x^2-3x-54=0 x=9 (pipes 9 h and 18 h). Third pipe =1/6-1/9=1/18 → 18 h. (3 h is 9 − 6.)

One pipe fills a tank 9 hours faster than another, and together they fill it in 6 hours. When a third pipe, which empties the tank, is also opened, the three fill the empty tank in 9 hours. How long does the third pipe take to empty the full tank?

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