At a party , each person shakes hands with every other person . the total number of hand shakes was 66. how many persons are present at the party ?
A 6 b 11 c 12 d 18 e 33
One line has people, so handshakes can take place.
Each person can shake hands with (x-1) other people,
hence there are handshakes possible
the factors of 132 that differ by 1 are 11 and 12, hence x=12, x-1=11.
12 people are at the party.