If each participant of a chess tournament plays exactly one game with each of the remaining participants, then 190 games will be played during the tournament. What is the number of participants?	Pick:  A) 14  B) 16  C) 18  D) 20  E) 22

Rationale: "let n be the number of participants . the number of games is nc 2 = n * ( n - 1 ) / 2 = 190 n * ( n - 1 ) = 380 = 20 * 19 ( trial and error ) the answer is d ."
Answer: D