Simple. Total probability = 1

So probability of a draw

= Total probability - probability of Tom winning - probability of Jerry winning

= 1 - 0.2 - 0.5
= 0.3

is it :
case 1: tom win aka jerry lose
case 2 : jerry win aka tom lose
case 3 : draw
total prob = 1

i was wondering about the losing case . is it implied

Yup, Tom wins implies Jerry loses in this case, since Tom is competing against Jerry and there must be a loser for every winner produced.

thanks :)

Yup your cases are correct. For a game of 2 players competing against each other, you can't have 2 winners per match/game.


The way the probability is given suggests that draws are possible in the game (eg. chess)

For other cases, there aren't draws (eg. Tic-tac-toe, carrom, Mario Kart). So if the combined probability of 1 party winning and the other party winning equals 1, the probability of a draw is nil.

great explanation as always