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Pipe A fills a tank of capacity 700 liters at the rate of 40

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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 01 Nov 2016, 06:32
What an amazing sum!

1 min work of Pipe A : 40 l.
1 min work of Pipe B : 30 l.
1 min work of Pipe C : -20 l.

3 min work : 50 l.

Notice how this is a cycle and not '1' unit of time work.

Thus, 13 'cycles' would make = 13*50l = 650l.
Now, Pipe A + Pipe B 1 minute work would fill in 70 litres.

Thus, 720 litres are filled (Hence it has to be under 41 minutes)
Thus, Answer : 40 minutes 20 seconds.
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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 01 Apr 2017, 00:21
Bunuel wrote:
aiming4mba wrote:
Pipe A fills a tank of capacity 700 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?


In three minutes net gain is 40+30-20=50 liters;

After 13 cycles (13*3=39 minutes) net gain will be 13*50=650 liters.

Then in 1 minute pipe A will add 40 liters, 10 liters to be filled;

Then to fill 10 liters pipe B will need 10/30=1/3 min.

So total time \(39+1+\frac{1}{3}=40\frac{1}{3}\) min.

Why this process is not working for below?

https://gmatclub.com/forum/pipe-a-and-p ... 80611.html

Pipe A and Pipe B fill water into a tank of capacity 1000 litres at the rate of 100 litres/minute and 25 litres/minute respectively. Pipe C drains water from the same tank at the rate of 50litres/minute. Pipe A is kept open for a minute and then closed, then pipe B is kept open for a minute and then closed, followed by a drain pipe C for a minute and then closed. This process is repeated until the tank is full. How long will it take to fill the tank.

A) 39 mins
B) 40 mins
C) 39 mins and 20 secs
D) 37 mins
E) 41 mins

In three minutes net gain is 100+25-50=75 liters;

After 13 cycles (13*3=39 minutes) net gain will be 13*75=975 liters.

Then to fill 25 liters pipe A will need 25/100=1/4 min.

So total time \(39+\frac{1}{4}\) min = 39 min 15 sec

But Answer is D.
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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 06 Jun 2017, 16:23
aiming4mba wrote:
Pipe A fills a tank of capacity 700 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?

A) 42 minutes
B) 14 minutes
C) 39 minutes
D) 40 minutes 20 seconds
E) None of these

1. In a cycle of 3 minutes, 40+30-20=50 liters are filled
2. In 13 such cycles, 13*50 = 650 liters are filled.
3. Then in the next fresh cycle, A fills 40 liters and 690 liters are filled.
4. The remaining 10 liters are filled by B in 20 seconds for a total time of 40 minutes 20 seconds
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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 03 Jul 2018, 05:38
aiming4mba wrote:
Pipe A fills a tank of capacity 700 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?

A) 42 minutes
B) 14 minutes
C) 39 minutes
D) 40 minutes 20 seconds
E) None of these



A = + 40 litres a minutes
B= + 30 litres a minute
C=-20 litres a minute

total transaction in 3 minutes
40+30-20=50 litres

600 litres in 6*6 = 36 minutes
670 litres in 38 minutes
650 litres in 39 minutes
690 in 40 minutes
need 10 more litres which is 1/3rd the rate of B
so 60/3=20 seconds
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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 03 Jul 2018, 10:41
Bunuel wrote:
aiming4mba wrote:
Pipe A fills a tank of capacity 700 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?


In three minutes net gain is 40+30-20=50 liters;

After 13 cycles (13*3=39 minutes) net gain will be 13*50=650 liters.

Then in 1 minute pipe A will add 40 liters, 10 liters to be filled;

Then to fill 10 liters pipe B will need 10/30=1/3 min.

So total time \(39+1+\frac{1}{3}=40\frac{1}{3}\) min.


can't we instead first figure out first 630 litres of the tank's capacity would get obtained in what time and add 2 more minutes to it ?
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Re: Pipe A fills a tank of capacity 700 liters at the rate of 40  [#permalink]

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New post 04 Jul 2018, 20:44
Bunuel wrote:
aiming4mba wrote:
Pipe A fills a tank of capacity 700 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?


In three minutes net gain is 40+30-20=50 liters;

After 13 cycles (13*3=39 minutes) net gain will be 13*50=650 liters.

Then in 1 minute pipe A will add 40 liters, 10 liters to be filled;

Then to fill 10 liters pipe B will need 10/30=1/3 min.

So total time \(39+1+\frac{1}{3}=40\frac{1}{3}\) min.




Question: It takes 3 mins (or 1 cycle by A, B, C) to fill 50 liters. How many mins to fill 700 liters (say x)? x = 700 x 3 / 50 = 42 mins?
Re: Pipe A fills a tank of capacity 700 liters at the rate of 40 &nbs [#permalink] 04 Jul 2018, 20:44

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