Five couples were at a party. If each person shook hands exactly once with everyone, how many handshakes were exchanged? (Note: One obviously doesn't shake hands with oneself.)
For N people.....the number of handshakes =
(N) ( N-1) / 2
So
(5) (5 - 1) /2 =
( 5 * 4) / 2 =
10 handshakes
IF couple 1 names A and so on,
A-B,C,D,E (4)
B-C,D,E (3)
C-D,E (2)
D-E (1)
1+2+3+4=10
Ans:10
