If $A$ and $B$ are two sets, then $A \cup B = A \cap B$ iff
Find the union of each of the following pairs of sets :
$A=\{1,2,3\}, B=\varnothing$
If $A$ and $B$ are two sets then $(A -B) \cup (B -A) \cup (A \cap B)$ is equal to
The shaded region in the given figure is
If $n(A) = 3$, $n(B) = 6$ and $A \subseteq B$. Then the number of elements in $A \cup B$ is equal to