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. none of these

Answer 1

Answer: (A)

373

$n\left(A\right)=115$

$n\left(B\right)=326$

$n(A-B)=47$

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

$=115-47=68$

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

$=115+326-68$

$=326+47$

$=373$

Option A.