Aptitude - Pipes and Cistern - Discussion

Discussion Forum : Pipes and Cistern - General Questions (Q.No. 3)
3.
A pump can fill a tank with water in 2 hours. Because of a leak, it took 2 hours to fill the tank. The leak can drain all the water of the tank in:
4 1 hours
3
7 hours
8 hours
14 hours
Answer: Option
Explanation:

Work done by the leak in 1 hour = 1 - 3 = 1 .
2 7 14

Leak will empty the tank in 14 hrs.

Discussion:
90 comments Page 4 of 9.

Hari said:   7 years ago
Assume they are 2 different pipes.
So total units of water to be filled is lcm of 2 and 7/3 =42units.
The leak takes 1/3time extra than 1st pipe.
So work done by the leak is 1/3 * 42 = 14.
(1)

Salman said:   7 years ago
Thanks @Ash.

Yamini Dhanasekar said:   7 years ago
@Jamsheed.

Always, we can consider total work be 1.
So
Hour ---- Work completed.
x ---- 1
3 ---- ?
By, cross multiplication,
3/X of the work.
Hope you understand.

Yamini Dhanasekar said:   7 years ago
It can also solved by;

Let the Filling pump be 'A' and leakage be 'B'.
A takes 2 hrs to fill, In 1 hr -it will complete 1/2 of the work, ie half of the tank.

In addition of B,
A-B=2 1/3 hrs, In 1 hr they complete 1/21/3 which is;
A-B=3/7.

We can substitute A,
1/2 -B=3/7
B=1/14.

So, In hr, B drains 1/14 part of the tank.
Total work-1.
Hr -- work
1 -- 1/14
? -- 1.

1/1/14= 14 hours.

Ashish said:   7 years ago
Good explanation. Thanks @Paushali Mukhoty.

Anil said:   7 years ago
Let consider 12-litre tank and pump fill in 2 hours(120 mins) w/o leakage.
with leakage, it takes 2 hours 20 mins,
means its take 20 mins extra,
so pump fill 2 litres extra in leakage condition,
total 14 litres fill by the pump but in tank 12 litres left,
means in 2hrs 20mins leakage leaks only 2 litres,
the total is 12 litres,
2 litres x6=12 litres.
7/3 hours(2 hrs 20 mins)x6 = 14 hours.

Rakesh said:   7 years ago
It takes 2 hours to fill the tank.

It takes 2 1/3 (7/3 hrs)hours to fill the tank including the leak.
Now,
Tank fill in 1 hour=1/2,
Tank fill in 1 hour including leak = 3/7,
Tank leak for 1 hour= tank fill in 1 hour- tank fill including tank leak in 1 hour = 1/2 - 3/7=1/14,
So, 1/14 of the tank will be empty in 1 hour.
Now, 1/14*14 of the tank will be empty in 1*14 hour. (Multiply 14 on both sides),
The Complete tank will be empty by leak in 14 hours.

Stella brown said:   7 years ago
How is 1/2-3/7 possible? Please explain indetail.

Manuj said:   7 years ago
From, where 2 1/3 came?

Jamsheed said:   7 years ago
Please tell me if a small pump drained a tank in x hours. In 3 hours how much it will drained?

Anyone solve this.


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