Problem: There are 20 people in the room, each person must shake hands with every other person in the room. How many handshakers were there?

This problem is Algorithm!


1st person---- shakes 19 hands
2nd person--- shakes 18 hands
3rd person--- shakes 17 hands
4th person--- shakes 16 hands
5th person--- shakes 15 hands
and so on until 20 people....

=A1*(A1-1)
answer is : 190