Question

If n(A) = 8 and n(B) = 6 and the sets A and B are disjoint, then find $n(A\cup B)$.

Answer 1

Given,

$n\left(A\right)=8,n\left(B\right)=6$

A and B are disjoint.

$⟹A\cap B=\varphi$

$⟹n(A\cap B)=0$

Now,

$n(A\cup B)=n\left(A\right)+n\left(B\right)-n(A\cap B)$

$n(A\cup B)=8+6-0=14$.