SOLUTION: Three pipes are connected to a water tank. One of the pipes can fill the tank in 30 min. The second pipe can fill it in 20 min. The third pipe can fill the tank in 40 min. If t

Question 170779: Three pipes are connected to a water tank. One of the pipes can fill the tank in 30 min. The second pipe can fill it in 20 min. The third pipe can fill the tank in 40 min. If the slowest pipe is shut off after 3 min and fastest is shut off 3 min later, how long will it take the remaining open pipe to finish filling the tank?
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
they each fill some FRACTION of the tank, based on their individual filling times

let x=remaining fill time __

multiplying by 120 __ 9+36+4x+24=120 __ 4x+69=120

subtracting 69 __ 4x=51

dividing by 4 __ x=51/4 __ x=12min 45sec
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