Question

Given n(J) = 285, n(K) = 197 and n(J ∪ K) = 431, find n(J ∩ K).

Answer 1

By the inclusion/exclusion principle,

n(J ∩ K) = n(J) + n(K) - n(J U K)

n(J ∩ K) = 285 + 197 - 431

n(J ∩ K) = 51