Mutually exclusive events can't both happen at once. Add their probabilities.
Rule
P(A or B) = P(A) + P(B)
Try it
Roll a die. P(getting 1 or 2)?
1/6 + 1/6 = 1/3.
Mutually exclusive events can't both happen at once. Add their probabilities.
Roll a die. P(getting 1 or 2)?
1/6 + 1/6 = 1/3.