Question

If n(U) = 50, n(A) = 20, $n\left(\right(A\cup B{)}^{\prime })$ = 18 then n(B - A) is

• A. $14$
• B. $12$
• C. $16$
• D. $20$

Answer 1

The correct option is B $12$

$n\left(U\right)=50,n\left(A\right)=20$

$n(A\cup B)=18$ $n(B-A)=?$

So, $n(A\cup B)=n\left(0\right)-n(A\cup B)$

So. $n(A\cup B)=32$

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

$=32-20$

$n(B-A)=12$