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basic combination

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basic combination

by joconnor » Thu Sep 22, 2011 7:33 am
Two members of a club are to be selected to represent the club at a national mtg. If there are 190 different possible selections of the 2 members, how many members does the club have?

a) 20
b) 27
c) 40
d) 57
e) 95
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by gmatclubmember » Thu Sep 22, 2011 7:53 am
joconnor wrote:Two members of a club are to be selected to represent the club at a national mtg. If there are 190 different possible selections of the 2 members, how many members does the club have?

a) 20
b) 27
c) 40
d) 57
e) 95
If there are n member in the club, then the combinations possible to choose 2 members would be nC2.
n(n-1)/2 = 190 = n(n-1)=19*20 =>n=20.

A is the OA.

Cheers
Ami/-
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