The Total Number of Reflexive Relations on a Finite Set Having n Elements is
Question
The total number of reflexive relations on a finite set having \( n \) elements is ……………………….
Solution
Let a finite set \( A \) have \( n \) elements.
Then the Cartesian product \( A \times A \) contains:
\[ n^2 \]
ordered pairs.
A relation on \( A \) is reflexive if:
\[ (a,a)\in R \quad \text{for all } a\in A \]
Thus, all diagonal elements:
\[ (a_1,a_1), (a_2,a_2), \ldots, (a_n,a_n) \]
must necessarily be included in the relation.
So, out of the \( n^2 \) ordered pairs:
- \( n \) pairs are fixed (must be included)
- Remaining \( n^2-n \) pairs may or may not be included
Hence, the total number of reflexive relations is:
\[ 2^{\,n^2-n} \]
Therefore, the required answer is:
\[ \boxed{2^{n^2-n}} \]