Last visit was: 31 May 2026, 08:53 It is currently 31 May 2026, 08:53
Home
Messages
MBA Fair
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: 30 May 2026
Posts: 110,986
Own Kudos:
818,069
 [4]
Given Kudos: 106,546
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: 110,986
Kudos: 818,069
 [4]
A and B can do a piece of work in 72 days; B and C can do it in 120 da 08 Feb 2021, 03:30
Kudos
Add Kudos
4
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:

35% (medium)

Question Stats:

75% (02:40) correct 25% (03:10) wrong based on 123 sessions

History

Date
Time
Result
Not Attempted Yet
A and B can do a piece of work in 72 days; B and C can do it in 120 days; A and C can do it in 90 days. In what time can A alone do it ?

(A) 150 days
(B) 120 days
(C) 100 days
(D) 80 days
(E) 70 days
ShowHide Answer
Official Answer
B
User avatar
imeanup
User avatar
Joined: 15 Jun 2017
Last visit: 24 Mar 2026
Posts: 452
Own Kudos:
638
 [1]
Given Kudos: 8
Location: India
Posts: 452
Kudos: 638
 [1]
A and B can do a piece of work in 72 days; B and C can do it in 120 da 08 Feb 2021, 21:45
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Ans B

Attach Screenshot
Attachments

Untitled2.png
Untitled2.png [ 15.37 KiB | Viewed 2849 times ]

User avatar
Geet03
User avatar
Joined: 03 Aug 2020
Last visit: 17 Jul 2025
Posts: 8
Own Kudos:
12
Given Kudos: 38
Posts: 8
Kudos: 12
A and B can do a piece of work in 72 days; B and C can do it in 120 da 13 Feb 2021, 00:10
Kudos
Add Kudos
Bookmarks
Bookmark this Post
meanup
Ans B

Attach Screenshot
Show more
Can you please explain how are we calculating efficiency?
avatar
igoaid
avatar
Current Student
Joined: 12 Aug 2020
Last visit: 15 Apr 2023
Posts: 4
Given Kudos: 130
Location: India
Schools: HEC MiM "23 (A) HEC Sept'22 Intake (A)
GMAT 1: 700 Q49 V35
GPA: 3.75
Schools: HEC MiM "23 (A) HEC Sept'22 Intake (A)
GMAT 1: 700 Q49 V35
Posts: 4
Kudos: 0
A and B can do a piece of work in 72 days; B and C can do it in 120 da 13 Feb 2021, 02:17
Kudos
Add Kudos
Bookmarks
Bookmark this Post
1/A + 1/B = 1/72 ----- (i)
1/B + 1/C = 1/120 ---- (ii)
Subtracting (i) and (ii)
1/A - 1/C = 1/180 ---- (iii)
1/A + 1/C = 1/90 ---- (iv)
Adding (iii) and (iv)
2/A = (1+2)/180 = 3/180 = 1/60
2/A = 1/60
1/A = 120
A = 120
User avatar
imeanup
User avatar
Joined: 15 Jun 2017
Last visit: 24 Mar 2026
Posts: 452
Own Kudos:
638
Given Kudos: 8
Location: India
Posts: 452
Kudos: 638
A and B can do a piece of work in 72 days; B and C can do it in 120 da 13 Feb 2021, 04:37
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Geet03
meanup
Ans B

Attach Screenshot
Can you please explain how are we calculating efficiency?
Show more

The efficiency of an individual? It is mentioned to the right in the pic. Firstly, we are calculating the combined efficiency, then we are substituting the eff. of an individual.

Geet03

Let me share another pic with complete detail and please tag me for any further clarification

Posted from my mobile device
Attachments

Untitled2.png
Untitled2.png [ 43.11 KiB | Viewed 2638 times ]

User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 39,166
Own Kudos:
1,126
Posts: 39,166
Kudos: 1,126
A and B can do a piece of work in 72 days; B and C can do it in 120 da 10 Feb 2024, 22:34
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.
Moderator:
Bunuel
Math Expert
110986 posts