19 people (a1,a2,......,a19) are invited to a party. The host and the hostess shake hands with each invitee and also with each other. The invitees shake hands in a circular fashion, i.e. the pairs (a1, a2), (a2, a3),......,(a18, a19), (a19, a1) shake hands. So, in all there are 58 handshakes. Let S be a set of people such that every pair in S shake hands. The size of S is at most
O 2
O 3
O 1
O 4

• 4
  
  set will have host, hostess and 2 guests standing together say a1.a2.
• 12 years agoHelpfull: Yes(18) No(1)