Question

If $A=\{1,2,3\},B=\{4,5,6,7,8\},$ $C=\{4,8,12,16,20\},$ then $n\left[\right(A\times B)\cup (A\times C\left)\right]=$

• A. $16$
• B. $24$
• C. $30$
• D. $12$

Answer 1

The correct option is B $24$

$A=\{1,2,3\},B=\{4,5,6,7,8\},$ $C=\{4,8,12,16,20\}$

$(A\times B)\cup (A\times C)=A\times (B\cup C)(B\cup C)=\{4,5,6,7,8,12,16,20\}$

$\therefore n\left[\right(A\times B)\cup (A\times C\left)\right]=n(A\times (B\cup C\left)\right)=n\left(A\right)\times n(B\cup C)=3\times 8=24$