Seven participants in a chess tournament, each played against each other once. How many games were played?

In a chess tournament with 7 participants, where each played one game against each other, the total number of games is calculated by the formula for the number of pairs of participants:

[ \frac{n , (n - 1)}{2} ]

where ( n = 7 ).

Substituting:

[ \frac{7 \times 6}{2} = \frac{42}{2} = 21 ]

A total of 21 games were played.