For 3 sets A, B, C: n(A ∪ B ∪ C) =
ARandom
BΣn(individual) - Σn(pairs) + n(A ∩ B ∩ C)
Cn(A) + n(B) + n(C)
Dn(A) × n(B) × n(C)
Answer & Solution
Correct answer: B. Σn(individual) - Σn(pairs) + n(A ∩ B ∩ C)
Inclusion-exclusion for 3 sets: n(A∪B∪C) = n(A) + n(B) + n(C) - n(A∩B) - n(A∩C) - n(B∩C) + n(A∩B∩C). Generalizes to n sets with alternating signs.
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