Question

If A and B are disjoint sets,then how can you find n(A union.B ).

Answer 1

By definition of disjoint set we mean that there won’t be any common elements in both the sets. Therefore A intersection B will be null.

Therefore, n(A intersection B)=0

In general, n(A union B) = n(A) + n(B) - n(A intersection B)

Since A and B are disjoint sets,

n(A union B) = n(A) + n(B)