In the set of natural numbers,the relation "is less than" is:

Let $A = \{1, 2, 3, 4, 6\}$. Let $R$ be the relation on $A$ defined by $R = \{(a, b) : a, b \in A, b \text{ is exactly divisible by } a\}$. Find the domain of $R$.

Let $R$ and $S$ be two equivalence relations on a set $A$. Then

If $R$ is an equivalence relation on a set $A$,then $R^{-1}$ is

Let $A = \{1, 2, 3\}$. The number of relations on $A$ containing $(1, 2)$ which are symmetric and transitive but not reflexive is . . . . . . .

Let $R$ and $S$ be equivalence relations on a set $A$. Then,