Question

If $n\left(A\right)=4$ and $n\left(B\right)=5$, then $n(A\times B)=$

• A. $20$
• B. $25$
• C. $4$
• D. $15$

Answer 1

The correct option is A $20$

Given, $n\left(A\right)=4$ and $n\left(B\right)=5$

$\Rightarrow n(A\times B)=n\left(A\right)\cdot n\left(B\right)$

$\Rightarrow n(A\times B)=4\cdot 5=20$

So, answer is $20$.