There are $$10$$ players in a chess tournament. If each game is played by $$2$$ players, and each player plays every other player exactly once, what is the total number of games played in the tournament? 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning->Sports Competition
There are $10$ players and each player plays $9$ games, so there are $10 \times 9 \div 2 = 45$ games in total. 