Question

If n(A)=11 and n(B)=18,find the maximum value of n(AnB).​

Answer 1

The maximum value of n (A ∩ B) occurs when A ⊂ B (i.e. when A is a subset of B), in which case A ∩ B = A, and so max{n (A ∩ B)} = n (A) = 11.