A Tennis championship is played on knockout basis i.e. a player is out of the tournament when he loses a match
Methods 1
2 player will play= 1 match
4 player will play= 1+2=3 match
8 player will play= 1+2+4=7 match
16 player will play= 1+2+4+8=15 match
32 player will play= 1+2+4+8+16=31 match
So, 32 players participated in the tournament if 31 matches are totally played
Method 2
N player will play = (N-1) Matches
So, (N+1) player will play = (N) Matches
32 players participated in the tournament if 31 matches are totally played