Question 1 :
Let $A$ and $B$ have $3$ and $6$ elements respectively. What can be the minimum number of elements in $A\cup B$?

Question 2 :
If sets $A$ and $B$ are given as $\displaystyle A=\left \{ x\mid x+4=4 \right \},B=\left \{ 0 \right \}$ then:

Question 3 :
<div><div>Observe the following sets and answer the question given below.</div><div>$A =$ The set of all the residents in Mumbai.</div><div>$B =$ The set of all the residents in Bhopal.</div><div>$C =$ The set of all the residents in Maharashtra.</div><div>$D =$ The set of all the residents in India.</div><div>$E =$ The set of all the residents in Madhya-Pradesh.</div></div><div><br/></div>Which set can be chosen suitably as the universal set

Question 5 :
Let $\displaystyle A=\left \{ 1,3,3,1\right \}$ and $B=\left \{ 1,4 \right \}$, then A and B are&#160;