Question

If $n(A)=115$, $n(B)=326$, $n(A-B)=47$, then $n(A\cup B)$ is equal to

• A. $373$
• B. $165$
• C. $370$
• D. $389$

Answer 1

Answer: (A)

$n(A)=m(A-B)+n(A\cap B)$ implies
$115=47+n(A\cap B)$
$\therefore n(A\cap B)=115-47=68$
$\therefore n(A\cup B)=n(A)+n(B)-n(A\cap B)$
$=115+326-68=373$