Question

If n(A) = 21, n(B) = 26, n(A ∩ B) = 14, then calculate n(A ∪ B)

Answer 1

The Inclusion Exclusion Principle

n(A U B) = n(A) + n(B) - n(A n B) .

n(A U B) = 21 + 26 - 14

n(A U B) = 33 (ans.)