A school hockey team plays a match. The probability of their winning is estimated to be 0.5 and the probability of losing 0.3. Explain why the probability of the team drawing must be 0.2.

In a match the only outcomes are winning, losing or drawing and these outcomes are mutually exclusive (i.e. a team cannot both win and lose a match).

The total probability of all possible outcomes is 1, therefore:

1−0.5−0.3 = 0.2