Question: how to calculate the intersection of two sets?
Answer: The general probability addition rule for the union of two events states that P(A∪B)=P(A)+P(B)−P(A∩B) P ( A ∪ B ) = P ( A ) + P ( B ) − P ( A ∩ B ) , where A∩B A ∩ B is the intersection of the two sets. The addition rule can be shortened if the sets are disjoint: P(A∪B)=P(A)+P(B) P ( A ∪ B ) = P ( A ) + P ( B ) .