2026-04-18

Problem — 2026-04-18

Easy

Easycombinatorics

A group of $10$ people are in a room. Each pair of people shakes hands exactly once. How many handshakes occur?

Enter an integer

Show solution

Each handshake involves choosing

2

people from

10

. The number of such pairs is

\binom{10}{2} = \frac{10 \cdot 9}{2} = 45