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# work

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Senior Manager
Joined: 05 Oct 2008
Posts: 267

Kudos [?]: 550 [0], given: 22

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25 Jan 2009, 12:10
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

6 machines take 12 days to complete a job. How many more machines will be needed to complete the job in 8 days?

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6

Kudos [?]: 550 [0], given: 22

GMAT Tutor
Joined: 24 Jun 2008
Posts: 1340

Kudos [?]: 2001 [0], given: 6

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25 Jan 2009, 12:19
The job requires 6*12 = 72 total days of machine work. So, one machine would do the job in 72 days, two machines in 36 days, three machines would need 24 days, etc. To do the job in 8 days, we'd need 9 machines in total, or 3 additional machines.
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Last edited by IanStewart on 25 Jan 2009, 15:56, edited 1 time in total.

Kudos [?]: 2001 [0], given: 6

Intern
Joined: 24 Jan 2009
Posts: 19

Kudos [?]: 2 [1], given: 0

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25 Jan 2009, 13:22
1
KUDOS
If 6 machines take 12 days to complete the task, one machine takes 72 days. Let X be number of machines and d the number of days:
$$\frac{x}{72}=\frac{1}{d}$$

What you want is for d to equal 8, so X must be nine and you'll need 3 more machines.
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All Day

Kudos [?]: 2 [1], given: 0

Intern
Joined: 19 Jan 2009
Posts: 17

Kudos [?]: 4 [0], given: 0

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27 Jan 2009, 10:39
6 machines take 12 days to complete a job. How many more machines will be needed to complete the job in 8 days?

2
3
4
5
6

This question is on inverse proportions.
Its btw number of machines and days.

so md = k ( constant)

6x12 = m x 8

6 x 12 / 8 = m

9 = m

how many more = 9 - 6 = 3

Kudos [?]: 4 [0], given: 0

Re: work   [#permalink] 27 Jan 2009, 10:39
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# work

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