How to find P(A or B) with the addition rule: add P(A) and P(B), then subtract P(A ∩ B), the overlap the sum counted twice. One card from a deck, a heart or a king, shows why. P(A ∪ B), the probability that event A or event B or both will occur, equals P(A) + P(B) − P(A ∩ B).
Sources
College Board, AP Statistics Course and Exam Description. AP Central, 2026.
Cited for: Topic 2.5, the intersection P(A ∩ B); topic 2.7, the union P(A ∪ B) and P(A ∪ B) = P(A) + P(B) − P(A ∩ B)
An original visual explanation. Animation made with sci_anim:
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Little fun fact or whatever: the -P(A and B) can be equal to 0