Addition Rule of Probability
The rule that P(A ∪ B) = P(A) + P(B) - P(A ∩ B), which gives the probability that at least one of the events A or B occurs.
Real World
Spotify calculates the probability a randomly chosen user listens to either pop or hip-hop using the addition rule, adjusting for listeners who enjoy both genres.
Exam Focus
Show P(A∩B) subtracted explicitly; omitting it is the most common error and costs the method mark.
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