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by WarrenGMAT
Tue Nov 23, 2010 4:51 pm
 
Forum: Manhattan Prep GMAT CAT Math
Topic: Siblings Problem - Combinatorics
Replies: 21
Views: 11715
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Re: Siblings Problem - Combinatorics

4/7 you pick someone with 1 sibling. 3/7 you pick someone with 2 siblings. If you pick a 1 sibling person, he has one sibling in the deck of 6 remaining people: 4/7 x 1/6 = 4/42 = 2/21 If you pick a 2 sibling person: 3/7 x 2/6 = 6/42 = 3/21 Add them: 5/21 says you get a sibling pair. 1 - 5/21 = 16/2...