Q.

Let A = {0, 1, 2, 3, 4, 5}. Let R be a relation on A defined by (x, y R if and only if max {x, y {3, 4}. Then among the statements

(S1) : The number of elements in R is 18, and

(S2) : The relation R is symmetric but neither reflexive nor transitive.           [2025]

1 both are true  
2 only (S2) is true  
3 both are false  
4 only (S1) is true  

Ans.

(2)

R = {(0, 3), (3, 0), (0, 4), (4, 0), (1, 3), (3, 1), (2, 3), (3, 2), (3, 3), (1, 4), (4, 1), (2, 4), (4, 2), (3, 4), (4, 3), (4, 4)}

   Number of elements in R = 16

   S1 is false.

Now, (0, 0), (1, 1), (2, 2), (5, 5)  R    R is not reflexive.

Again, let (a, b R then (b, a R

As max {a, b} = max {b, a}    R is symmetric.

Now, R is not transitive as (0, 3), (3, 1)  R but (0, 1)  R.

   S2 is true.