Question

BRAIN TEASER: At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?

Answer 1

If you know permutations and combinations you can do this in one step, do you know it?

Answer 2

Yep.

Answer 3

what do you think it is?

Answer 4

Then, it will be nC2=66, since a handshake consists of any two persons shaking hands with each other.

Answer 5

If you simplify that, it would come as a quadratic equation as follows :