Two members of a certain club are selected to speak at the next club meeting. If there are 45 different possible selections of the 2 club members, how many members does the club have?	Choose one
A) 5  B) 6  C) 7  D) 8  E) 10
Method-1   Total No. of Selection of r out of n objects are defined by nCr = n! / [(r!)(n-r)!]   i.e. If total member = n   then nC2 = n! / [(2!)(n-2)!] = 45   i.e. n*(n-1)*n-2!/ [(2!)n-2!] = 45   i.e. n*(n-1) = 90   (for Positive Values of n)   therefore, n*(n-1) = 90   i.e. n= 10   Answer: Option 10
<result>E</result>
Two members of a certain club are selected to speak at the next club meeting. If there are 45 different possible selections of the 2 club members, how many members does the club have?