Final answer:
A casual ping-pong match can vary in length, but a competitive match is usually a best-of-seven series, with each game played to 11 points and requiring a two-point margin to win.
Step-by-step explanation:
The number of games played in a ping-pong match varies depending on whether it is a casual game or a competitive match. In casual play, players might agree on any number of games to determine a winner. However, in a competitive match, a match is typically played best out of any odd number of games, most commonly a best-of-five or best-of-seven.
In official table tennis competitions, such as those governed by the International Table Tennis Federation (ITTF), matches are usually played as a best-of-seven games series, with each game played to 11 points. A player must win by at least a two-point margin if the score reaches 10-10. Thus, a player must win four games to win a competitive seven-game match.