If each participant of a chess tournament plays exactly one game with each of the remaining participants, then 231 games will be played during the tournament. What is the number of participants? Choose one:
A) 16
B) 18
C) 20
D) 22
E) 24
Let n be the number of participants.   The number of games is nC2 = n*(n-1) / 2 = 231   n*(n-1) = 462 = 22*21 (trial and error)   The answer is 22.
<result>D</result>
If each participant of a chess tournament plays exactly one game with each of the remaining participants, then 231 games will be played during the tournament. What is the number of participants?