Question

If there are 12 persons in a party, and if each two of them shake hands with each other, how many handshakes happen in the party?

Answer 1

"When First person shakes hands of the other nine then Second person shakes hands with the eight people they haven't yet and Third person with remaining seven shakes hands.

So, 9+8+7+6+5+4+3+2+1 = 45

There are 12 people in a set chooses the subset of two different ""elements"" where order does not matter.

Also, we need to choose all such subsets because each person is shaking hands with everyone else exactly once.

"

Answer 2

Answer:

p(n,r)=n!/(n-r)!

p(12,2)=12!/(12-2)!

=12x11x10!/10!

=12x11

132

Step-by-step explanation:

repetition is allowed.so, A handshakes with B and B also handshaking with A

(A,B)(B,A)