Wowem and men committes

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 38
Joined: Fri Aug 07, 2015 3:06 am
Thanked: 1 times

Wowem and men committes

by yass20015 » Mon Aug 10, 2015 11:23 am
Hi, I got this one from testprep:
There are 11 women and 9 men in a certain club. If the club is to select a committee of 2 women and 2 men, how many different sub-committes are possible?
The answer is 1980.
Why ? and is there any difference between committees and sub-commitees? Thanks
Source: — Problem Solving |

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Aug 10, 2015 11:48 am
I believe that the problem should read as follows:
There are 11 women and 9 men in a certain club. If the club is to select a committee of 2 women and 2 men, how many different such committees are possible?

A. 120
B. 720
C. 1,060
D. 1,520
E. 1,980
Women:
Number of options for the first woman = 11. (Any of the 11 women.)
Number of options for the second woman = 10. (Any of the 10 remaining women.)
To combine these options, we multiply:
11*10.
Since the ORDER of the women does not matter -- AB constitutes the same pair of women as BA -- we DIVIDE by the number of ways the two women can be ARRANGED (2!):
(11*10)/(2*1) = 55.

Men:
Number of options for the first man = 9. (Any of the 9 men.)
Number of options for the second man = 8. (Any of the 8 remaining men.)
To combine these options, we multiply:
9*8.
Since the ORDER of the men does not matter -- CD constitutes the same pair of men as DC -- we DIVIDE by the number of ways the two men can be ARRANGED (2!):
(9*8)/(2*1) = 36.

To combine our 55 options for the 2 women and our 36 options for the 2 men, we MULTIPLY:
55*36 = 1980.

The correct answer is E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Mon Aug 10, 2015 1:18 pm
There are 11 women and 9 men in a certain club. If the club is to select a committee of 2 women and 2 men, how many different such committees are possible?

A. 120
B. 720
C. 1,060
D. 1,520
E. 1,980
Take the task of creating the committees and break it into stages.

Stage 1: Select two women for the committee
Since the order in which we select the women does not matter, we can use combinations.
We can select 2 women from 11 women in 11C2 ways (55 ways)
So, we can complete stage 1 in 55 ways

If anyone is interested, we have a free video on calculating combinations (like 11C2) in your head: https://www.gmatprepnow.com/module/gmat-counting?id=789

Stage 2: Select two men for the committee
Since the order in which we select the men does not matter, we can use combinations.
We can select 2 men from 9 men in 9C2 ways (36 ways)
So, we can complete stage 2 in 36 ways

By the Fundamental Counting Principle (FCP), we can complete the two stages (and thus create a 4-person committee) in (55)(36) ways ([spoiler]= 1980 ways[/spoiler])

Answer: E
--------------------------

Note: the FCP can be used to solve the MAJORITY of counting questions on the GMAT. For more information about the FCP, watch our free video: https://www.gmatprepnow.com/module/gmat-counting?id=775

Then you can try solving the following questions:

EASY
- https://www.beatthegmat.com/what-should- ... 67256.html
- https://www.beatthegmat.com/counting-pro ... 44302.html
- https://www.beatthegmat.com/picking-a-5- ... 73110.html
- https://www.beatthegmat.com/permutation- ... 57412.html
- https://www.beatthegmat.com/simple-one-t270061.html
- https://www.beatthegmat.com/mouse-pellets-t274303.html


MEDIUM
- https://www.beatthegmat.com/combinatoric ... 73194.html
- https://www.beatthegmat.com/arabian-hors ... 50703.html
- https://www.beatthegmat.com/sub-sets-pro ... 73337.html
- https://www.beatthegmat.com/combinatoric ... 73180.html
- https://www.beatthegmat.com/digits-numbers-t270127.html
- https://www.beatthegmat.com/doubt-on-sep ... 71047.html
- https://www.beatthegmat.com/combinatoric ... 67079.html


DIFFICULT
- https://www.beatthegmat.com/wonderful-p- ... 71001.html
- https://www.beatthegmat.com/ps-counting-t273659.html
- https://www.beatthegmat.com/permutation- ... 73915.html
- https://www.beatthegmat.com/please-solve ... 71499.html
- https://www.beatthegmat.com/no-two-ladie ... 75661.html
- https://www.beatthegmat.com/laniera-s-co ... 15764.html

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image