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# 6 workers should finish a job in 8 days. After 3 days came 4

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6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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26 May 2013, 08:20
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6 workers should finish a job in 8 days. After 3 days came 4 workers join them. How many days do they need to finish the same job?

A. 3
B. 4
C. 5
D. 6
E. 7

I do not have the OA. sorry for the inconvenience....
[Reveal] Spoiler: OA

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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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26 May 2013, 08:36
Expert's post
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atalpanditgmat wrote:
6 workers should finish a job in 8 days. After 3 days came 4 workers join them. How many days do they need to finish the same job?

A. 3
B. 4
C. 5
D. 6
E. 7

I do not have the OA. sorry for the inconvenience....

There are 6*8=48 units of work to be done (1 unit done by 1 worker in 1 day).

After 3 days 3*6=18 units are done and 30 units left to be done.

Now, 6+4=10 workers can do 30 units of the work in 30/10=3 days.

Hope it's clear.
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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26 May 2013, 09:06
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Let Rate of one worker be R
=> (6*R)*8 = 1 (Rate * Time = work)
=> R = 1/48
=> Work remaining after 3 days
1 - (3*6)/48 = 30/48

After 4 ppl joined in
((6+4)*Time)/48 = 30/48
Time = 3 days to finish the task
IMO A
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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19 Jun 2013, 11:17
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I agree with the math of both of the previous answers, just a question regarding wording: the question asks for "How many days do they need to finish the same job?," which in my mind is the 3 days that the 6 workers use, PLUS the 3 days that the 10 workers use, making the answer D. Thoughts?
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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19 Jun 2013, 11:33
Completely agree with Jeffcarl... I got 3+3 =6 days...

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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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19 Jun 2013, 14:36
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jeffcarl wrote:
I agree with the math of both of the previous answers, just a question regarding wording: the question asks for "How many days do they need to finish the same job?," which in my mind is the 3 days that the 6 workers use, PLUS the 3 days that the 10 workers use, making the answer D. Thoughts?

I originally picked D as well, for the same reason.. but after reviewing it again.

"how many days do they need to finish the same project?"

well the project as a whole takes 6 days, but only 3 days left to finish it.
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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20 Jun 2013, 03:06
dave785 wrote:
jeffcarl wrote:
I agree with the math of both of the previous answers, just a question regarding wording: the question asks for "How many days do they need to finish the same job?," which in my mind is the 3 days that the 6 workers use, PLUS the 3 days that the 10 workers use, making the answer D. Thoughts?

I originally picked D as well, for the same reason.. but after reviewing it again.

"how many days do they need to finish the same project?"

well the project as a whole takes 6 days, but only 3 days left to finish it.

Yes, that's correct. The question asks: "how many days do they need to finish the same job?"
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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08 Jun 2015, 03:02
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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20 Jun 2015, 01:47
Can someone pls review my approach?

6 workers need 8 days for a job. This implies that one worker's rate is 8 / 6 = 4 / 3.

Rate of one worker = 4 / 3 times the new number of workers (6+4 = 10):
4/3 * 10 = 40/3 is the rate for all workers.

Take the reciprocal: 3 / 40 implies that they need 3 weeks for the work of 40.

Is this correct or did i just got lucky? Thanks!
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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20 Jun 2015, 02:50
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noTh1ng wrote:
Can someone pls review my approach?

6 workers need 8 days for a job. This implies that one worker's rate is 8 / 6 = 4 / 3.

Rate of one worker = 4 / 3 times the new number of workers (6+4 = 10):
4/3 * 10 = 40/3 is the rate for all workers.

Take the reciprocal: 3 / 40 implies that they need 3 weeks for the work of 40.

Is this correct or did i just got lucky? Thanks!

You have made a sever mistake of this topic in the calculation you have shown
6 workers need 8 days for a job. This implies that one worker's rate is 8 / 6 = 4 / 3.

The highlighted part is a flaw in your process. The correct Understanding of the highlighted part is as mentioned below

6 workers need 8 days for a job. This implies that one worker's rate is 8 * 6 = 48 days to finish the same job

The reason for this interpretation is Manpower is Inversely Proportional to the Time.

CONCEPT:i.e. more manpower causes less time to finish the job and Less manpower requires more time to finish the job

Work can be finished in 8 days
Remaining Days = 8-3 = 5 days

Now, 6 workers are joined by 4 more workers i.e. the Manpower Increases from 6 to 10 i.e. 5/3 of previous workforce

therefore New time taken should be reciprocal (Inversely Proportional) i.e. 3/5 of previous time i.e. New time = (5)*(3/5) = 3 days

So they Require 3 more days to finish the work.
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Re: 6 workers should finish a job in 8 days. After 3 days came 4 [#permalink]

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23 Dec 2016, 05:43
Hello from the GMAT Club BumpBot!

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Re: 6 workers should finish a job in 8 days. After 3 days came 4   [#permalink] 23 Dec 2016, 05:43
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