Cardinal number of some sets - Practice Questions & MCQ

The number of distinct elements in a finite set A is called the Cardinal number of set A and it is denoted by $\mathrm{n}(\mathrm{A})$.
For example, if set $A=\{1,3,7,11,13\}$ then $n(A)=5$

Given, any two finite sets A and B, then the Number of Elements in the union of sets A \& B is given by $n(A \cup B)=n(A)+n(B)-n(A \cap B)$

If $(A \cap B)=\varphi$, then $n(A \cup B)=n(A)+n(B)$

Given A, B, and C are any finite sets, then the Number of Elements in the union of sets A, B \& C is given by

$\mathrm{n}(\mathrm{A} \cup \mathrm{B} \cup \mathrm{C})=\mathrm{n}(\mathrm{A})+\mathrm{n}(\mathrm{B})+\mathrm{n}(\mathrm{C})-\mathrm{n}(\mathrm{A} \cap \mathrm{B})-\mathrm{n}(\mathrm{B} \cap \mathrm{C})-\mathrm{n}(\mathrm{A} \cap \mathrm{C})+\mathrm{n}(\mathrm{A} \cap \mathrm{B} \cap \mathrm{C})$