Last visit was: 20 Nov 2025, 08:38 It is currently 20 Nov 2025, 08:38
Home
GMAT
Messages
Tests
Schools
Events
Rewards
Chat
My Profile
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 20 Nov 2025
Posts: 105,420
Own Kudos:
778,546
 [29]
Given Kudos: 99,987
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,420
Kudos: 778,546
 [29]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 22 Apr 2020, 06:50
Kudos
Add Kudos
28
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

55% (hard)

Question Stats:

72% (02:50) correct 28% (03:07) wrong based on 245 sessions

History

Date
Time
Result
Not Attempted Yet
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. The pipes are opened simultaneously but it turns out that the tank is defective and has a hole at the bottom. Because of that it takes 48 minutes extra to fill the tank. When the tank is full, the pipes are closed. In how many hours will the tank be emptied due to the hole?

A. 60 hrs
B. 72 hrs
C. 84 hrs
D. 96 hrs
E. 112 hrs


Are You Up For the Challenge: 700 Level Questions
ShowHide Answer
Official Answer
B
Most Helpful Reply
User avatar
yashikaaggarwal
User avatar
Senior Moderator - Masters Forum
Joined: 19 Jan 2020
Last visit: 17 Jul 2025
Posts: 3,086
Own Kudos:
3,103
 [5]
Given Kudos: 1,510
Location: India
Schools: Cranfield (A) Warwick MiM "23 (M)
GPA: 4
WE:Analyst (Internet and New Media)
Schools: Cranfield (A) Warwick MiM "23 (M)
Posts: 3,086
Kudos: 3,103
 [5]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 22 Apr 2020, 07:24
5
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Answer is B. 72 hours
Take LCM of 12&18=36 litres
Therefore A fills 3litre/hour
And B fills 2litre/hour.
Total 5litre/hour.
And 36litre will be filled in 7.2 hours that is 7 hours and 12 min. (1/5*60 for minutes) -----(1)
Since the tank has leakage it's taking 7hours and 12 minutes+ 48 minutes that is 8 hours to fill tank.
Before tank was filling at the rate of 5litre/hour so it took 7.2 hours. Now we have time we have to draw out how many litres is put into tank per hour which is to be filled in 8 hours.
36/8=4.5 so the tank is in taking 4.5 litre / hour which will lead the tank to be filled in 8 hours.
Since the tap is not closed or tempered in between. So 0.5 litre per hour minus is the leakage. (3+2-0.5)=4.5 litres.
Now it takes 1hour to drain 0.5litre from tank.
36litre tank would be drained in 36/0.5 hours. That is 72.
So OA is B option

Posted from my mobile device
User avatar
lacktutor
User avatar
Joined: 25 Jul 2018
Last visit: 23 Oct 2023
Posts: 659
Own Kudos:
1,398
 [5]
Given Kudos: 69
Posts: 659
Kudos: 1,398
 [5]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 22 Apr 2020, 14:26
4
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
Bunuel
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. The pipes are opened simultaneously but it turns out that the tank is defective and has a hole at the bottom. Because of that it takes 48 minutes extra to fill the tank. When the tank is full, the pipes are closed. In how many hours will the tank be emptied due to the hole?

A. 60 hrs
B. 72 hrs
C. 84 hrs
D. 96 hrs
E. 112 hrs


Are You Up For the Challenge: 700 Level Questions
Show more

\(\frac{1}{12} + \frac{1}{18}= \frac{1}{y}\)

\(\frac{1}{12} + \frac{1}{18} - \frac{1}{x} = \frac{1}{(y+ 4/5)}\)

---> x= ???
----------------------------------------------------------------------------------------------------------------------------------
\(\frac{3+2}{36}= \frac{1}{y}\) --> \(y = \frac{36}{5}\)

--->\(\frac{1}{12} + \frac{1}{18} - \frac{1}{x} = \frac{1}{(36/5+ 4/5)}= \frac{1}{8}\)

--> \(\frac{1}{x} = \frac{1}{12} + \frac{1}{18} - \frac{1}{8}= \frac{(6+ 4- 9)}{72}\)

\(x= 72 \)

Answer (B).
General Discussion
User avatar
eakabuah
User avatar
Retired Moderator
Joined: 18 May 2019
Last visit: 15 Jun 2022
Posts: 776
Own Kudos:
1,126
 [3]
Given Kudos: 101
Posts: 776
Kudos: 1,126
 [3]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 22 Apr 2020, 10:39
2
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
The two pipes working together will take\( \frac{12*18}{(12+18)} = \frac{12*18}{30} = \frac{36}{5} hrs\) to fill the tank if there is no leak.
Due to the leak, the time taken, \(Tef = \frac{36}{5}+\frac{48}{60} = \frac{36}{5}+\frac{4}{5} = 8 hrs\).
But \(1/\frac{36}{5}-\frac{1}{Lt}=\frac{1}{8}\) where \(Lt=\)time taken for a full tank to be emptied by the leak on the tank.
\(\frac{1}{Lt}=\frac{5}{36}-\frac{1}{8} = \frac{10-9}{72} = \frac{1}{72}\)
Hence \(Lt=72 \)hours

The answer is B.
User avatar
CrackverbalGMAT
User avatar
Major Poster
Joined: 03 Oct 2013
Last visit: 20 Nov 2025
Posts: 4,844
Own Kudos:
8,946
 [1]
Given Kudos: 225
Affiliations: CrackVerbal
Location: India
Expert
Expert reply
Posts: 4,844
Kudos: 8,946
 [1]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 22 Apr 2020, 23:44
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
Let the capacity of the tank (work to be done) be 360 litres. Although 36 is the LCM of 12 and 18, taking 360 (basically a bigger multiple of 36) is to ensure that we don't have to deal with fractions at a later stage in the problem.

Pipe 1 can fill it in 12 hours, therefore it fills at the rate of 30 litres per hour.
Pipe 2 can fill it in 18 hours, therefore, it fills at the rate of 20 litres per hour.

When they work together, they fill at the rate of 50 litres per hour. If the hole was not present, they would have filled the tank in \(\frac{360 }{ 50}\) hours i.e. 7.2 hours i.e. 7 hours 12 mins.
With the hole being present at the bottom of the tank, it took 48 minutes more i.e. it took 8 hours. Therefore, the tank must have been filled at an effective rate of 45 litres per hour since \(\frac{360 }{ 8}\) = 45.

The rate of emptying should hence be 5 litres per hour. To empty 360 litres, the hole will take \(\frac{360}{5}\) = 72 hours.

The correct answer option is B.

Hope that helps!
User avatar
ScottTargetTestPrep
User avatar
Target Test Prep Representative
Joined: 14 Oct 2015
Last visit: 20 Nov 2025
Posts: 21,720
Own Kudos:
27,004
Given Kudos: 300
Status:Founder & CEO
Affiliations: Target Test Prep
Location: United States (CA)
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 21,720
Kudos: 27,004
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 24 Apr 2020, 08:54
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. The pipes are opened simultaneously but it turns out that the tank is defective and has a hole at the bottom. Because of that it takes 48 minutes extra to fill the tank. When the tank is full, the pipes are closed. In how many hours will the tank be emptied due to the hole?

A. 60 hrs
B. 72 hrs
C. 84 hrs
D. 96 hrs
E. 112 hrs

Show more

The normal fill rate (i.e, if there is no hole in the tank) is 1/12 + 1/18 = 3/26 + 2/36 = 5/36. Thus, it will take 1/(5/36) = 36/5 hours to fill the tank normally.

Now, let’s let x = the number of hours it takes the full tank to empty due to the hole. Thus, we can create the equation (notice that 48 minutes = 48/60 = 4/5 hour):

1/(5/36 - 1/x) = 36/5 + 4/5

1/(5/36 - 1/x) = 8

5/36 - 1/x = 1/8

Multiplying the equation by 72x, we have:

10x - 72 = 9x

x = 72

Answer: B
User avatar
SanjaySrini
User avatar
Joined: 08 Sep 2019
Last visit: 04 Nov 2025
Posts: 82
Own Kudos:
53
Given Kudos: 38
Location: India
Schools: IESE '24 LBS '22
GMAT Focus 1: 705 Q88 V87 DI80
GMAT 1: 730 Q50 V40
Products:
My Reviews
Schools: IESE '24 LBS '22
GMAT Focus 1: 705 Q88 V87 DI80
GMAT 1: 730 Q50 V40
Posts: 82
Kudos: 53
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 24 Apr 2020, 18:20
Kudos
Add Kudos
Bookmarks
Bookmark this Post
lacktutor
Bunuel
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. The pipes are opened simultaneously but it turns out that the tank is defective and has a hole at the bottom. Because of that it takes 48 minutes extra to fill the tank. When the tank is full, the pipes are closed. In how many hours will the tank be emptied due to the hole?

A. 60 hrs
B. 72 hrs
C. 84 hrs
D. 96 hrs
E. 112 hrs


Are You Up For the Challenge: 700 Level Questions

\(\frac{1}{12} + \frac{1}{18}= \frac{1}{y}\)

\(\frac{1}{12} + \frac{1}{18} - \frac{1}{x} = \frac{1}{(y+ 4/5)}\)

---> x= ???
----------------------------------------------------------------------------------------------------------------------------------
\(\frac{3+2}{36}= \frac{1}{y}\) --> \(y = \frac{36}{5}\)

--->\(\frac{1}{12} + \frac{1}{18} - \frac{1}{x} = \frac{1}{(36/5+ 4/5)}= \frac{1}{8}\)

--> \(\frac{1}{x} = \frac{1}{12} + \frac{1}{18} - \frac{1}{8}= \frac{(6+ 4- 9)}{72}\)

\(x= 72 \)

Answer (B).
Show more

Thank you for the solution.
User avatar
Lipun
User avatar
Joined: 05 Jan 2020
Last visit: 08 Jan 2025
Posts: 144
Own Kudos:
157
 [2]
Given Kudos: 291
Posts: 144
Kudos: 157
 [2]
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 17 Jun 2020, 08:54
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
A fills tank in 12 hrs. B fills tank in 18 hrs.

Together they can fill the tank in (12*18)/(12+18) = 36/5 hrs

But because of the leak, they take 48 extra mins to fill the tank. 48 mins = 4/5 hrs

In 1hr they fill 5/36 parts of the tank, so in 4/5 hrs they'll fill 1/9 parts of the tank. This is the extra amount they need to fill because of the leak.

This means 1/9 parts of the tank leaks every 8 hours.

So for the full tank to be empty it will take 9*8 = 72 hours
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,600
Own Kudos:
1,079
Posts: 38,600
Kudos: 1,079
Two pipes can fill an empty tank in 12 hrs and 18 hrs, respectively. T 25 Nov 2024, 08:12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderators:
Bunuel
Math Expert
105420 posts
Krunaal
Tuck School Moderator
805 posts