# 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
Explanation:

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

Leak will empty the tank in 14 hrs.

Discussion:
85 comments Page 1 of 9.

DILIP KUMAR B K said:   2 years ago
As we know that rate (r)=work(w)/time(t).

Here the main thing is the work will remain constant.

Therefore,

As we have to find the time taken to empty the tank that is (T) with the leak will be;
W/T = (W/2 - W/(7/3)).

Cancelling "w" on both sides.

1/T = (1/2 - 3/7) = 1/14.
To get T,

We reciprocate the above result which is T = 14 hrs.
(7)

KALAISELVAN E said:   3 years ago

Thanks for explaining.
(1)

Vivek anand said:   3 years ago
Guys, it's simple.

First thing;
A pump can fill water in 2 hours.
Due to the leak, it takes 2 1/3 hours.

They are asking in how many hours it can empty the tank through leak only.

So,
1. Tap ---> 2 hours.
2. Tap+leak ---> 2 1/3 hours (i.e) 7/3 hours.
3. Leak ---> ?

Leak = ( tap + leak ) - tap
= 1/7/3 - 1/2.
= 3/7 - 1/2,
= 6-7/14,
= -1/14.
Total leak = -14 - indicates leak or outlet etc.
(43)

Appu said:   3 years ago
Shortcut;

x = 2.
y = 7/3 =====>(2 * 3) + 1.
x*y/y-x =====>14.
(2)

Messi said:   3 years ago
Thanks for explaining @Suresh.

Suresh said:   3 years ago
Convert Hours into minutes.

A can fill in 2hrs i.e 120mins.
Leakage i.e a-b 2 1/3 is equal to 140mins.
Then capacity (LCM) is 840.

Efficiency : A is 7 and a-b is 6 and the difference is 1.

It can empty one part per minute out of 840 minutes. Then 840 parts can be emptied in 840 minutes.

Now convert 840 minutes to hours.

840/60 is 14 hours.
(12)

R.Jana said:   3 years ago
How to do by using the ratio process? Please explain.
(1)

Dhivyanisan said:   3 years ago
Time is taken by pump without leak = 2hrs.
Its discharge capacity says a= 1/2.
Time is taken by a pump with leak = 2 (1/3)hrs or 7/3 hrs.
It's discharge capacity say b= 1/(7/3) = 3/7.
So discharge capacity of the leak is a-b = 1/14.
Time taken by the leak to empty tank = 1/(1/14) = 14 hrs.

SUDHARSHAN NAIDU said:   3 years ago
The efficiency of a pipe in 1 hour is 1/2 = 0.5lit/h.
The efficiency of a pipe with leakage 1/2.33 = 0.429,
The difference between 0.5 - 0.429 is 0.07.
The efficiency of a leak is 0.07lits/ hour.
So, check with an option in how many hours the 1-litre tank empty we get the answer.

Reddy said:   3 years ago
How 3/7 with leakage? Explain, please.