1.  In a chess tournament each of six players will play every other player exactly once. How many matches will be played during the tournament ?
A. 12
B. 15
C. 30
D. 36

Answer: Option B

Explanation:

I. matches of first player with other 5 players

II. matches of second player with 4 players other than the first player

III. matches of third player with 3 players other than the first player and second player.

IV. matches of fourth player with 2 players other than the first player, second player and third player.

V. matches of fifth player with 1 player other than the first player, second player, third player and fourth player.

So total matches will be 5+4+3+2+1 = 15