Last visit was: 09 May 2026, 15:56 It is currently 09 May 2026, 15:56
Home
Messages
Tests
Schools
Events
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: 09 May 2026
Posts: 110,221
Own Kudos:
813,908
 [11]
Given Kudos: 106,141
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: 110,221
Kudos: 813,908
 [11]
Two hoses (A and B) are filling a pool. Working alone at their individ 08 Oct 2018, 07:14
Kudos
Add Kudos
10
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

35% (medium)

Question Stats:

69% (01:34) correct 31% (01:50) wrong based on 382 sessions

History

Date
Time
Result
Not Attempted Yet
Two hoses (A and B) are filling a pool. Working alone at their individual constant rates Hose A could fill the pool in 6 hours, and Hose B could do it in 4 hours. If Hose A works alone for one hour and then Hose B joins after that, how long will it take in total for the pool to be filled?

A. 2 hours
B. 2 hours, 12 minutes
C. 2 hours, 48 minutes
D. 3 hours
E. 3 hours, 12 minutes
ShowHide Answer
Official Answer
D
User avatar
Abhishek009
User avatar
Board of Directors
Joined: 11 Jun 2011
Last visit: 17 Dec 2025
Posts: 5,902
Own Kudos:
5,463
 [2]
Given Kudos: 463
Status:QA & VA Forum Moderator
Location: India
GPA: 3.5
WE:Business Development (Commercial Banking)
Posts: 5,902
Kudos: 5,463
 [2]
Two hoses (A and B) are filling a pool. Working alone at their individ 08 Oct 2018, 08:31
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
Two hoses (A and B) are filling a pool. Working alone at their individual constant rates Hose A could fill the pool in 6 hours, and Hose B could do it in 4 hours. If Hose A works alone for one hour and then Hose B joins after that, how long will it take in total for the pool to be filled?

A. 2 hours
B. 2 hours, 12 minutes
C. 2 hours, 48 minutes
D. 3 hours
E. 3 hours, 12 minutes
Show more

Let the capacity of the Pool be 12 units

So, Efficiency of Hose A is 2 units/hour & Efficiency of Hose B is 3 units/hour

Work completed by A in 1 hour is 2 units, so 10 Units of work is left

Combined efficiency of A & B is 5 units/hour.

So, The time taken to fill 10 units is 10/5 = 2 Hours

Thus, the total time taken to fill the Pool will be 1 + 2 = 3 Hours, Answer must be (D)
User avatar
Salsanousi
User avatar
Joined: 19 Oct 2013
Last visit: 29 Dec 2020
Posts: 390
Own Kudos:
358
 [2]
Given Kudos: 117
Location: Kuwait
GPA: 3.2
WE:Engineering (Real Estate)
Posts: 390
Kudos: 358
 [2]
Two hoses (A and B) are filling a pool. Working alone at their individ 08 Oct 2018, 08:31
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
Well if hose A’s rate is 1/6

So in 1 hour it will fill 1/6 of the pool.


Remaining work is 6/6 - 1/6 = 5/6

Now the combined rate is 1/4 + 1/6 = 5/12

Since time = work/rate = (5/6)/(5/12) = 2 hours

2 hours is the time needed for the two hoses combined to fill 5/6 of the pool.

Total time = 1 hour + 2 hours = 3 hours.

Answer choice D.

Posted from my mobile device
avatar
Weido
avatar
Joined: 25 Jul 2018
Last visit: 26 Nov 2018
Posts: 8
Own Kudos:
12
Given Kudos: 107
Posts: 8
Kudos: 12
Two hoses (A and B) are filling a pool. Working alone at their individ 08 Oct 2018, 08:34
Kudos
Add Kudos
Bookmarks
Bookmark this Post
A needs 6h for the complete pool, so in 1h A fills 1/6 of the pool
B work rate is 1/4
A+B together have a rate of = 1/6 + 1/4= 10/24= 5/12

Formula = R*T=W . 5/12*X = 1-1/6 units of pool that still needs to be filled up

5/12 * X =5/6 --> X=5/6*12/5 --> X=2 so after A has worked one hour, both together need additional 2 hours. This results in 3hours in total for filling the pool.

Hence, D
User avatar
MathRevolution
User avatar
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Last visit: 27 Sep 2022
Posts: 10,063
Own Kudos:
20,055
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Expert
Expert reply
GMAT 1: 760 Q51 V42
Posts: 10,063
Kudos: 20,055
Two hoses (A and B) are filling a pool. Working alone at their individ 05 Sep 2021, 23:53
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Pipe A in 1 hour will fill \(\frac{1}{6} ^{th}\) part of pool.

The remaining part of \(\frac{5}{6}\) will be filled by both A and B at the together rate of \(\frac{1}{6} + \frac{1}{4} = \frac{5}{12}\)

So, to fill the \(\frac{5}{6}\) part of the pool together at the rate of \(\frac{5}{12}\), both A and B will take 2 hours.

Total time taken : 1 + 2 = 3 hours

Answer D
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 39,042
Own Kudos:
1,123
Posts: 39,042
Kudos: 1,123
Two hoses (A and B) are filling a pool. Working alone at their individ 19 Jun 2023, 04:53
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Bunuel
Math Expert
110221 posts
Krunaal
Tuck School Moderator
852 posts