A Cistern has an inlet pipe and outlet pipe. The inlet pipe fills the cistern completely in 1 hour 20 minutes when the outlet pipe is plugged. The outlet pipe empties the tank completely in 4 hours when the inlet pipe is plugged. If both pipes are opened simultaneously at a time when the tank was one-third filled, when will the tank fill thereafter?
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Answer:
80 Mins
Step-by-step explanation:
The inlet pipe fills the cistern completely in 1 hour 20 minutes
=> 80 Mins
=> tank filled in 1 Min = 1/80
he outlet pipe empties the tank completely in 4 hours
=> 240 mins
=> Tank emptied in 1 Min = 1/240
Both pipe together Tank filled = 1/80 - 1/240
= (3 - 1)/240
= 2/240
= 1/120
Tank filled by both pipe in 120 mins
Tank is 1/3 filled already
so 1 - 1/3 = 2/3 tank will be filled in = (2/3)*120 = 80 Mins
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