Questions on Word Problems: Miscellaneous Word Problems answered by real tutors!

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an inlet pipe can fill a tank in 1 hour, a drain pipe can empty it in 3/2 hours. The inlet pipe was opened at 6:00 a.m. to fill the tank. At 6:20a.m. someone noticed that the drain has been left open and so he closes it immediately. How long will it take the first pipe to finish filling
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Filling pipe rate = 1 job/hour
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Draining pipe rate = 3/2 job/hour
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Together rate: 1-3/2 = -(1/2) job/hour
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EQUATION:
Both were operating from 6:00am till 6:20am or 1/3 hour.
In that time the tank would stay empty because the drain
pipe is removing water as fast as the inlet pipe puts it
in.
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The inlet pipe will then take 1 hour to fill the tank.
It should be full at 7:20 am.
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Cheers,
Stan H.

You can put this solution on YOUR website!
An inlet pipe can fill a tank in 1 hour; a drain pipe can empty it in 3/2 hours. The inlet pipe was opened at 6:00 a.m. to fill the tank. At 6:20 a.m. someone noticed that the drain has been left open and so he closes it immediately. How long will it take the first pipe to finish filling.
:
Let's deal in minutes here:
Inlet time = 60 min
Drain time = 90 min
:
let t = time (in minutes) required to finish filling the tank.
:
Let the full tank = 1:
:
Total on time for the inlet pipe = (t+20)
On time for the drain = 20 min
:
- = 1
Multiply equation by 180 to get rid of the denominators, results:
3(t+20) - 2(20) = 180
:
3t + 60 - 40 = 180
3t + 20 = 180
3t = 180 - 20
3t = 160
t =
t = 53.333 min or 53 min 20 sec to finish filling the tank
:
:
Check with calc (inlet time: 53.33 + 20 = 73.33)
(73.33/60) - (20/90) = 1