Answer:
14365
Explanation:
If there are 170 people, total, then each one shakes hands with 169 other people.
You’d think that would mean 170 x 169 handshakes, or 28730. But each handshake counts twice, because two people are involved, right? So you need to divide that number by two.
(This works because handshaking is commutative — if I’m shaking your hand, then you’re shaking my hand. If we used some other action that was not commutative, such as giving a punch to the nose, then the answer would indeed be 28730.)
So take that number and divide it by two.