Two members of a club are to be selected to represent the club at a national meeting. if there are 153 different possible selections of the 2 members, how many members does the club have?
Choose the correct choice from the following answers.
A) 20  B) 27  C) 40  D) 18  E) 95
I have done this problem by substituting numbers   We have n!/2!(n-2)! =153   or n(n-1)/2 = 153 or n^2 -n =306 or (n-18) (n+17)=0   n=18 satisfies the equation   18
<result>D</result>
Two members of a club are to be selected to represent the club at a national meeting. if there are 153 different possible selections of the 2 members, how many members does the club have?