Cub Scout PS

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edvhou812: Master | Next Rank: 500 Posts; Posts: 143; Joined: Sat Nov 06, 2010 9:06 pmFollowed by: 1 member; Thanked: 10 times

by edvhou812 » Tue Mar 22, 2011 10:17 pm

Five Cub Scouts are in a den; A, B, C, D and E. A has a Bobcat Badge, B has a Wolf Badge, C has a Bear Badge, D is a slacker that only has a bunch of Gold Arrows, and E wishes that he was a Girl Scout. If two are selected from this group to sell a fund raising item, what are the odds that the group will include one scout that has an animal based badge, and that the group will end up selling cookies?

A: 2/10
B: 2/5
C: 19/20
D: 3/20
E: 5/2

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Source: Beat The GMAT — Problem Solving | Tue Mar 22, 2011 10:17 pm

HSPA: Legendary Member; Posts: 1101; Joined: Fri Jan 28, 2011 7:26 amFollowed by: 13 members; Thanked: 47 times; GMAT Score:640

by HSPA » Tue Mar 22, 2011 10:32 pm

The question is a lot american: My assumptions
only girl scout can sell cookies

Number of ways of selecting 2 in 5 = 5C2
One animal badge and 1 girl scout = 3C1+1 : D is named a slacker

so 4/10 = 2/5 .. now we need to find the odds against this

IMO E. ( I am having very little confidence on my solution)

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AIM GMAT: Legendary Member; Posts: 857; Joined: Wed Aug 25, 2010 1:36 amFollowed by: 15 members; Thanked: 56 times

by AIM GMAT » Tue Mar 22, 2011 10:38 pm

I totally agree with HSPA , going ahead with same assumption .

IMO D.

(3/5) X (1/4) = 3/20

3 ppl with animal badge so 3/5
1 person wanna be girl scout so 1/4 [1 person is already selected so 4 left]

Thanks & Regards,
AIM GMAT

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manpsingh87: Master | Next Rank: 500 Posts; Posts: 436; Joined: Tue Feb 08, 2011 3:07 amFollowed by: 6 members; Thanked: 72 times

by manpsingh87 » Tue Mar 22, 2011 10:42 pm

edvhou812 wrote:Five Cub Scouts are in a den; A, B, C, D and E. A has a Bobcat Badge, B has a Wolf Badge, C has a Bear Badge, D is a slacker that only has a bunch of Gold Arrows, and E wishes that he was a Girl Scout. If two are selected from this group to sell a fund raising item, what are the odds that the group will include one scout that has an animal based badge, and that the group will end up selling cookies?

A: 2/10
B: 2/5
C: 19/20
D: 3/20
E: 5/2

out of five scouts any two scouts can be selected in 5C2 ways.

now as the group must include one animal based badge so out of 3 people the one with animal badge be selected in 3C1,as no restriction is placed upon the second selection therefore out of the remaining two persons one can be selected in 2C1 ways.

therefore required probability would be 1 - P(favour) = 1- 3C1*2C1/5C2;
1-3/5=2/5
hence B

O Excellence... my search for you is on... you can be far.. but not beyond my reach!

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