Answer
When two events (A, B) are mutually exclusive, we have P(A and B)=0
so the addition rule 2 becomes P(A or B) = P(A)+ P(B) which is the same as
addition Rule 1 and can be used for this case.
Work Step by Step
Addition Rule 1:
When two events A and B are mutually exclusive, the probability that A or B will occur is
P(A or B)= P(A) + P(B)
Addition Rule 2:
If A and B are not mutually exclusive, then
P(A or B) = P(A)+ P(B) - P(A and B)
