If the king and queen invite 8 knights and thier wives then how many handshakes will there be if each couple cannot handshake with their lifetime partner. (I think this involves the king and queen as a couple).

Answer 1

Pick any person. There are 16 people to shake hands with.

Since there are 18 people, there are 18*16 shakes. But, counting this way, each shake is counted twice, once for each person. So, the final answer is

18*16/2