Question

If $A$ and $B$ are finite sets and $A\subset B,$ then

• A. $n(A\cup B)=n\left(A\right)$
• B. $n(A\cap B)=n\left(B\right)$
• C. $n(A\cup B)=n\left(B\right)$
• D. $n(A\cap B)=\varphi$

Answer 1

The correct option is C $n(A\cup B)=n\left(B\right)$

$A\subset B\text{As}A\text{is a subset of}B\text{so all the elements of}A\text{are present in}B\Rightarrow n(A\cup B)=n\left(B\right)\&n(A\cap B)=n\left(A\right)$