Question

A={1,2,3,4},b={2,4,6,8}find n(A union b)

Answer 1

n(AUB) = n(A)+n(B)-n(AΠB). (Π=intersection)
n(A)=4
n(B)=4
n(AΠB)=2 (because 2,4 are there on both A and B sets)
n(AUB) = 4+4-2
= 8-2
=6