Question

If A and B are disjoint sets, then n(A union B) =​

Answer 1

Given that A and B are disjoint sets.

$\implies A\cap B =\phi\\\implies n(A\cap B) = 0$

Here,

$n(A\cup B) = n(A) + n(B) - n(A\cap B)\\= n(A)+n(B) - 0\\\therefore n(A\cup B) = n(A) + n(B)$