Set, Relations and FunctionsPYQ Dec. 22Question 1945 of 217
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Let A={1,2,3}\displaystyle A = \{1, 2, 3\} and consider the relation R={(1,1),(2,2),(3,3),(1,2),(2,3),(1,3)}\displaystyle R = \{(1,1), (2,2), (3,3), (1,2), (2,3), (1,3)\} then R\displaystyle R is:

Options

ASymmetric and transitive
BReflexive but not transitive
CReflexive but not symmetric
DNeither symmetric, nor transitive
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Correct Answer

✅ Option c — Reflexive but not symmetric

All Options:

  • ASymmetric and transitive
  • BReflexive but not transitive
  • CReflexive but not symmetric
  • DNeither symmetric, nor transitive

Detailed Solution & Explanation

We are given set A={1,2,3}\displaystyle A = \{1, 2, 3\} and relation R={(1,1),(2,2),(3,3),(1,2),(2,3),(1,3)}\displaystyle R = \{(1,1), (2,2), (3,3), (1,2), (2,3), (1,3)\}.
Let's test the properties of R\displaystyle R:
1. **Reflexive**: For R\displaystyle R to be reflexive, every element a∈A\displaystyle a \in A must satisfy (a,a)∈R\displaystyle (a, a) \in R.
Since (1,1),(2,2),(3,3)∈R\displaystyle (1, 1), (2, 2), (3, 3) \in R, R\displaystyle R is reflexive.
2. **Symmetric**: For R\displaystyle R to be symmetric, (a,b)∈R  ⟹  (b,a)∈R\displaystyle (a, b) \in R \implies (b, a) \in R.
Here, (1,2)∈R\displaystyle (1, 2) \in R but (2,1)∉R\displaystyle (2, 1) \notin R. Thus, R\displaystyle R is not symmetric.
3. **Transitive**: For R\displaystyle R to be transitive, (a,b)∈R and (b,c)∈R  ⟹  (a,c)∈R\displaystyle (a, b) \in R \text{ and } (b, c) \in R \implies (a, c) \in R.
Let's check:
- (1,2)∈R\displaystyle (1, 2) \in R and (2,3)∈R  ⟹  (1,3)∈R\displaystyle (2, 3) \in R \implies (1, 3) \in R. (True)
Therefore, R\displaystyle R is transitive.
Thus, the relation R\displaystyle R is reflexive and transitive, but not symmetric.
Hence, **Option C** is the correct answer.

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