If $X = \{ {4^n} - 3n - 1:n \in N\} $ and $Y = \{ 9(n - 1):n \in N\} ,$ then $X \cup Y$ = . . . . .
$X$
$Y$
$N$
None of these
If $S$ and $T$ are two sets such that $S$ has $21$ elements, $T$ has $32$ elements, and $S$ $\cap \,T$ has $11$ elements, how many elements does $S\, \cup$ $T$ have?
If $A$ and $B$ are two sets such that $A \subset B$, then what is $A \cup B ?$
If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find
$B \cap C$
State whether each of the following statement is true or false. Justify you answer.
$\{2,6,10,14\}$ and $\{3,7,11,15\}$ are disjoint sets.
Find the union of each of the following pairs of sets :
$A=\{1,2,3\}, B=\varnothing$