Which of the following pairs of sets are disjoint?
$A = \{a, e, i, o, u\}$ and $B = \{c, d, e, f\}$

If $A$ and $B$ are disjoint sets,then $n(A \cup B) = $

Find the union of each of the following pairs of sets:
$A = \{ x : x \text{ is a natural number and } 1 < x \le 6 \}$
$B = \{ x : x \text{ is a natural number and } 6 < x < 10 \}$

If $A=\{3, 5, 7, 9, 11\}, B=\{7, 9, 11, 13\}, C=\{11, 13, 15\}$ and $D=\{15, 17\}$; find $A \cap (B \cup D)$.

Find the intersection of the given pair of sets:
$X = \{1, 3, 5\}, Y = \{1, 2, 3\}$

Which Venn diagram represents the truth of the statement "All students are hard working."
Where $U$ = Universal set of human beings,$S$ = Set of all students,$H$ = Set of all hard workers.