no of groups

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no of groups

by ash4gmat » Sat Aug 27, 2016 3:17 am
Q.Of the 12 temp employees in a certain company,4 will be hired as perm employees.If 5 of the 12 temp employees are women,how many of the possible groups of 4 temp employees consist of 3 women and 1 man.
1.22
2.35
3.56
4.70
5.105

OA is D

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by GMATGuruNY » Sat Aug 27, 2016 3:40 am
Of the 12 temporary employees in a certain company, 4 will be hired as permanent employees. If 5 of the 12 temporary employees are women, how many of the possible groups of 4 employees consist of 3 women and one man?

A. 22
B. 35
C. 56
D. 70
E. 105
Since 5 of the 12 temporary employees are women, 7 are men.
Number of ways to choose 1 man from 7 options = 7C1 = 7.
Number of ways to choose 3 women from 5 options = 5C3 = (5*4*3)/(3*2*1) = 10.
To combine the options above, we multiply:
7*10 = 70.

The correct answer is D.
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by Brent@GMATPrepNow » Sat Aug 27, 2016 6:30 am
Of the 12 temporary employees in a certain company, 4 will be hired as permanent employees. If 5 of the 12 temporary employees are women, how many of the possible groups of 4 employees consist of 3 women and one man?

A. 22
B. 35
C. 56
D. 70
E. 105
Take the task of selecting the employees and break it into stages.

Stage 1: Select the 3 women
The order in which we select the women does not matter, so we can use combinations.
We can select 3 women from 5 women in 5C3 ways (= 10 ways)

Aside: If anyone is interested, we have a free video on calculating combinations (like 5C3) in your head: https://www.gmatprepnow.com/module/gmat-counting?id=789

Stage 2: Select the 1 man
There are 7 men, so we can complete this stage in 7 ways.

By the Fundamental Counting Principle (FCP), we can complete the two stages (and thus select the permanent employees) in (10)(7) ways ([spoiler]= 70 ways[/spoiler])

Answer: D
--------------------------

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by ash4gmat » Sun Aug 28, 2016 2:22 am
Dear Experts,

The question posted by me mentions of how many of the possible groups of 4 TEMPORARY employees consist of 3 women and 1 man.

We dont know what is the breakup of man & woman for temporary employees after 4 are made permanent.

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by ash4gmat » Sun Aug 28, 2016 5:42 am
Experts comment please.
ash4gmat wrote:Dear Experts,

The question posted by me mentions of how many of the possible groups of 4 TEMPORARY employees consist of 3 women and 1 man.

We dont know what is the breakup of man & woman for temporary employees after 4 are made permanent.

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by DavidG@VeritasPrep » Sun Aug 28, 2016 5:58 am
ash4gmat wrote:Dear Experts,

The question posted by me mentions of how many of the possible groups of 4 TEMPORARY employees consist of 3 women and 1 man.

We dont know what is the breakup of man & woman for temporary employees after 4 are made permanent.
The initial post was mis-worded. Look at Mitch's and Brent's cleaned up version. (There are 12 temporary employees, 4 of whom will be selected to become permanent employees.)
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by ash4gmat » Sun Aug 28, 2016 6:18 am
David if 4 permanent employees have no significance then why it is mentioned in the question?
DavidG@VeritasPrep wrote:
ash4gmat wrote:Dear Experts,

The question posted by me mentions of how many of the possible groups of 4 TEMPORARY employees consist of 3 women and 1 man.

We dont know what is the breakup of man & woman for temporary employees after 4 are made permanent.
The initial post was mis-worded. Look at Mitch's and Brent's cleaned up version. (There are 12 temporary employees, 4 of whom will be selected to become permanent employees.)

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by DavidG@VeritasPrep » Mon Aug 29, 2016 8:00 am
David if 4 permanent employees have no significance then why it is mentioned in the question?
It's just mentioned to give the 4-person group a label, but the label is incidental to the calculation. In essence, we have a pool of 5 women and 7 men. From this pool we want to know how many ways we can form a 4-person group of 3 women and 1 man. It just happens to be the case that those 4 people are being selected to become permanent employees. If those 4 people were being selected to form a dodgeball team or to go to the moon, etc., the math would be the same.
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by Scott@TargetTestPrep » Tue Aug 30, 2016 3:42 pm
ash4gmat wrote:Q.Of the 12 temp employees in a certain company,4 will be hired as perm employees.If 5 of the 12 temp employees are women,how many of the possible groups of 4 temp employees consist of 3 women and 1 man.
1.22
2.35
3.56
4.70
5.105

OA is D
Since 5 of the 12 temp employees are women, there are 7 male temp employees. We need to determine the number of possible groups of 4 temp employees that will consist of 3 women and 1 man. Since we have 5 female temp employees and we need to pick 3 of them, the number of ways we can do this is 5C3 since the order of their selection doesn't matter. Similarly, since we have 7 male temp employees and we need to pick only 1 of them, the number of ways we can do this is 7C1. Finally, to find number of possible groups of 4 temp employees that will consist of 3 women and 1 man, we multiply 5C3 and 7C1:

5C3 x 7C1 = (5 x 4 x 3)/(3 x 2 x 1) x 7 = 10 x 7 = 70

Answer: D

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by Matt@VeritasPrep » Thu Sep 01, 2016 4:59 pm
ash4gmat wrote:Dear Experts,

The question posted by me mentions of how many of the possible groups of 4 TEMPORARY employees consist of 3 women and 1 man.

We dont know what is the breakup of man & woman for temporary employees after 4 are made permanent.
It wouldn't matter, since they're all equally likely.

The question as you posted it was poorly written, since the first sentence is actually redundant. (The workers haven't yet been made permanent (they *will* be hired), so we're simply asked to find the number of groups of the 12 current temps that consist of 3 women and 1 man.)