Probability

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moneyman: Master | Next Rank: 500 Posts; Posts: 468; Joined: Sat Mar 03, 2007 10:17 pm; Thanked: 5 times

by moneyman » Thu Oct 30, 2008 9:55 am

Can anyone who has used the Manhattan GMAT Probability guide give me an approach taught by the book?

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Maxx

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Source: Beat The GMAT — Problem Solving | Thu Oct 30, 2008 9:55 am

earth@work: Master | Next Rank: 500 Posts; Posts: 248; Joined: Mon Aug 11, 2008 9:51 am; Thanked: 13 times

by earth@work » Thu Oct 30, 2008 10:17 am

Total ways=8c3=56 ways
now, let us take ways in which a couple is always present in committee, for this let us take couples as one object
i.e. Ways when couple present in committee = 4c1*6c1 =24
Ways when no couple present = 56-24 =32
IMO E=32

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mbaapplicant2008: Senior | Next Rank: 100 Posts; Posts: 42; Joined: Thu Oct 30, 2008 1:21 am

by mbaapplicant2008 » Thu Oct 30, 2008 7:18 pm

Yes, the answer is E.

MBA Applicant

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Thu Oct 30, 2008 8:23 pm

Can u explain a little more please on the 4c1*6c1?

now, let us take ways in which a couple is always present in committee, for this let us take couples as one object
i.e. Ways when couple present in committee = 4c1*6c1 =24

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earth@work: Master | Next Rank: 500 Posts; Posts: 248; Joined: Mon Aug 11, 2008 9:51 am; Thanked: 13 times

by earth@work » Sun Nov 02, 2008 6:18 pm

cramya wrote:Can u explain a little more please on the 4c1*6c1?

now, let us take ways in which a couple is always present in committee, for this let us take couples as one object
i.e. Ways when couple present in committee = 4c1*6c1 =24

Hi cramya, sorry for delayed reply.
4c1*6c1 .....
the 4c1 parts comes from considering couples as one object i.e instead of 8 people we consider 4 people only... ways to selects 1 out of 4 is 4c1 (this will give us couple in committee of 3
we are left with 3rd place in the committe to be filled by any remaining 6 people = 6c1
therefore , total ways when atleast one couple is present =4c1*6c1 =24
hope its clear now

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sun Nov 02, 2008 8:48 pm

Thanks Earth@work!

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