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# time and work

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Intern
Joined: 24 Jun 2009
Posts: 1

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24 Jun 2009, 03:09
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This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If a+b can perform a task in 12 days and b+c does the same in 20 days. How long will a+b+c take to complete the same task? Also deduce the indivisual performance.

Kindly show me the procedure to solve the same.
Manager
Joined: 10 May 2009
Posts: 63

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24 Jun 2009, 04:44
I tried a different approach of picking numbers:

Let's say A and B take 24 hours each to complete I unit of tasks

1/24 + (1/24) = 1/12

Hence for B and C:
1/24 + (1/C)=1/20

Therefor C will take 120 hours to finish 1 unit of job

There A,B and C will take:
1/12 + 1/120 = 11/120

Hence total hours : 120/11

Is this approach correct?!
Current Student
Joined: 12 Jun 2009
Posts: 1794
Location: United States (NC)
Concentration: Strategy, Finance
Schools: UNC (Kenan-Flagler) - Class of 2013
GMAT 1: 720 Q49 V39
WE: Programming (Computer Software)

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24 Jun 2009, 08:48
prinits wrote:
I tried a different approach of picking numbers:

Let's say A and B take 24 hours each to complete I unit of tasks

1/24 + (1/24) = 1/12

Hence for B and C:
1/24 + (1/C)=1/20

Therefor C will take 120 hours to finish 1 unit of job

There A,B and C will take:
1/12 + 1/120 = 11/120

Hence total hours : 120/11

Is this approach correct?!

I dont think it works? if i plug in 1/18 for A, 1/36 for B i get 45 for C and diff. answer....
_________________

Current Student
Joined: 03 Aug 2006
Posts: 112

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24 Jun 2009, 11:43
I think your question is missing information for A and C i.e. 'time for A and C' to be able to solve the problem.

Here is a link to a similar problem
ps-word-rate-problem-80051.html
Senior Manager
Joined: 23 Jun 2009
Posts: 355
Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago

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25 Jun 2009, 03:13
A and C needed. There are 3 variables and only two equations.
Re: time and work   [#permalink] 25 Jun 2009, 03:13
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