Question

Two sets such that $n(B-A)=25;n(A-B)=15$ and $n(A\cap B)=10,$ then $n(A\cup B)=$

• A. $30$
• B. $40$
• C. $50$
• D. $80$

Answer 1

The correct option is C $50$

Given $n(A-B)=15;n(B-A)=25$
and $n(A\cap B)=10$
Using the formula:
$n(A\cup B)=n(A-B)+n(B-A)+n(A\cap B)$
$\Rightarrow n(A\cup B)=15+25+10=50$