bMutually exclusive/b events cannot happen at the same time.

For example, rolling 1 or 2 on a dice is mutually exclusive.

For mutually exclusive events:

(P(A~\text{or}~B) = P(A∪B) = P(A) + P(B) )

[b]uMutually exclusive events[/u]/b

(P(A∪B) = P(A) + P(B) )