Q.

Let R be the relation in the set {1, 2, 3, 4} given by R = {(1, 2), (2, 2), (1, 1), (4, 4), (1, 3), (3, 3), (3, 2)}. Choose the correct answer: 

1 R is reflexive and symmetric but not transitive  
2 R is reflexive and transitive but not symmetric  
3 R is symmetric and transitive but not reflexive  
4 R is an equivalence relation  

Ans.

(2)

Ans.    R is reflexive and transitive but not symmetric.

Explanation:

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

It is seen that (a,a)∈R, for every a∈{1,2,3,4}

∴  R is reflexive.

It is seen that (1,2)∈R,but (2,1)∉R.

∴  R is not symmetric.

Also, it is observed that (a,b), (b,c)∈R ⇒(a,c)∈R, for all a,b,c∈{1,2,3,4}.

∴  R is transitive.

Hence,  R is reflexive and transitive but not symmetric.