Last visit was: 28 Apr 2026, 10:25 It is currently 28 Apr 2026, 10:25
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
Events & Promotions
Back to Forum
Create Topic
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 28 Apr 2026
Posts: 109,950
Own Kudos:
811,744
 [3]
Given Kudos: 105,927
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: 109,950
Kudos: 811,744
 [3]
A, B, and C together can do a work in 3 days. If A or B alone can do 27 Apr 2021, 06:45
Kudos
Add Kudos
3
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:

15% (low)

Question Stats:

80% (01:14) correct 20% (01:31) wrong based on 163 sessions

History

Date
Time
Result
Not Attempted Yet
A, B, and C together can do a work in 3 days. If A or B alone can do the work in 8 days, then how long will C take alone to do the same work?

(A) 27 days
(B) 12 days
(C) 5 days
(D) 2 days
(E) 1 day
ShowHide Answer
Official Answer
B
User avatar
Nidzo
User avatar
Joined: 26 Nov 2019
Last visit: 02 Aug 2025
Posts: 958
Own Kudos:
1,479
 [1]
Given Kudos: 59
Location: South Africa
Posts: 958
Kudos: 1,479
 [1]
A, B, and C together can do a work in 3 days. If A or B alone can do 27 Apr 2021, 07:06
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
1/a + 1/b + 1/c = 1/3

Sub in 1/a = 1/8 and 1/b = 1/8 into the above sum

1/8 + 1/8 + 1/c = 1/3
2/8 + 1/c = 1/3
1/c = 1/3 - 2/8
1/c = 8/24 - 6/24
1/c = 2/24
1/c = 1/12

Therefore answer B.
User avatar
LipiSinha
User avatar
Joined: 19 Jan 2016
Last visit: 13 Feb 2026
Posts: 66
Own Kudos:
94
Given Kudos: 57
Location: India
Schools: ISB '20
GMAT 1: 650 Q44 V37
GPA: 3.5
Schools: ISB '20
GMAT 1: 650 Q44 V37
Posts: 66
Kudos: 94
A, B, and C together can do a work in 3 days. If A or B alone can do 27 Apr 2021, 11:46
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Let the total units of work be 24

A, B and C together complete 8 units in one day

A alone completes 3 units in 1 day
B alone finishes 3 units in 1 day
So, C will complete (8-3+3) = 2 units in 1 day.

C alone will take 12 days to complete the work.

The answer will be B.
User avatar
imeanup
User avatar
Joined: 15 Jun 2017
Last visit: 24 Mar 2026
Posts: 452
Own Kudos:
636
Given Kudos: 8
Location: India
Posts: 452
Kudos: 636
A, B, and C together can do a work in 3 days. If A or B alone can do 27 Apr 2021, 23:15
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Ans B 12 Days

Screenshot
Attachments

Untitled.png
Untitled.png [ 9.24 KiB | Viewed 6302 times ]

User avatar
ScottTargetTestPrep
User avatar
Target Test Prep Representative
Joined: 14 Oct 2015
Last visit: 28 Apr 2026
Posts: 22,289
Own Kudos:
26,545
 [1]
Given Kudos: 302
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: 22,289
Kudos: 26,545
 [1]
A, B, and C together can do a work in 3 days. If A or B alone can do 15 Jul 2021, 10:03
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
A, B, and C together can do a work in 3 days. If A or B alone can do the work in 8 days, then how long will C take alone to do the same work?

(A) 27 days
(B) 12 days
(C) 5 days
(D) 2 days
(E) 1 day
Show more
Solution:

We know that the daily rate of A alone is 1/8, and the daily rate of B alone is also 1/8. If we let c = the number of days it takes C to complete the work alone, we can create the equation:

1/8 + 1/8 + 1/c = 1/3

Multiplying the equation by 24c, we have:

3c + 3c + 24 = 8c

24 = 2c

12 = c

Answer: B
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,986
Own Kudos:
1,119
Posts: 38,986
Kudos: 1,119
A, B, and C together can do a work in 3 days. If A or B alone can do 15 Oct 2024, 17:08
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
109950 posts
Krunaal
Tuck School Moderator
852 posts