$6 \cdot 9$ Suppose there are $n$ teams participating in a volleyball tournament, and the tournament is conducted in a knockout (elimination) format. In the tournament, every two teams that meet play one match, and each match must have a winner and a loser, with the losing team being eliminated from the tournament. How many matches will be played in total by the time the champion is determined?
[Solution] In each match, exactly 1 team exits the competition. By the time the champion team is determined, a total of $n-1$ teams have exited the competition, which of course means that a total of $n-1$ matches have been played.