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Sets and Relations question

2004 · Shift 0 · Q116
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Sets and Relations question

2004 · Shift 0 · Q116

JEE MainMathematicsSets and RelationsMCQ+4 / −1
Let R={(1,3),(4,2),(2,4),(2,3),(3,1)}R=\{(1,3),(4,2),(2,4),(2,3),(3,1)\}R={(1,3),(4,2),(2,4),(2,3),(3,1)} be a relation on the set A={1,2,3,4}A=\{1,2,3,4\}A={1,2,3,4}. The relation RRR is :
  1. A
    a function
  2. B
    transitive
  3. C
    not symmetric
  4. D
    reflexive
View written solutionFree

Correct answer: C

  1. Given relation

    R={(1,3),(4,2),(2,4),(2,3),(3,1)}R=\{(1,3),(4,2),(2,4),(2,3),(3,1)\}R={(1,3),(4,2),(2,4),(2,3),(3,1)} on A={1,2,3,4}.A=\{1,2,3,4\}.A={1,2,3,4}.

    We check each option one by one.

  2. Option A: Is RRR a function?

    For a relation on AAA to be a function from AAA to AAA, each element of AAA must have exactly one image.

    From the relation:

    • 1↦31 \mapsto 31↦3
    • 2↦42 \mapsto 42↦4 and 2↦32 \mapsto 32↦3
    • 3↦13 \mapsto 13↦1
    • 4↦24 \mapsto 24↦2

    Since the element 222 has two images (444 and 333), RRR is not a function.

    So, A is false.

  3. Option B: Is RRR transitive?

    A relation is transitive if whenever (a,b)∈R(a,b) \in R(a,b)∈R and (b,c)∈R(b,c) \in R(b,c)∈R, then (a,c)∈R(a,c) \in R(a,c)∈R must also be in RRR.

    Check a counterexample:

    • (1,3)∈R(1,3) \in R(1,3)∈R
    • (3,1)∈R(3,1) \in R(3,1)∈R

    Then transitivity would require: (1,1)∈R(1,1) \in R(1,1)∈R But (1,1)∉R(1,1) \notin R(1,1)∈/R.

    Hence, RRR is not transitive.

    So, B is false.

  4. Option C: Is RRR not symmetric?

    A relation is symmetric if whenever (a,b)∈R(a,b) \in R(a,b)∈R, then (b,a)∈R(b,a) \in R(b,a)∈R also belongs to RRR.

    Check the pairs:

    • (1,3)∈R(1,3) \in R(1,3)∈R and (3,1)∈R(3,1) \in R(3,1)∈R ✔️
    • (4,2)∈R(4,2) \in R(4,2)∈R and (2,4)∈R(2,4) \in R(2,4)∈R ✔️
    • (2,3)∈R(2,3) \in R(2,3)∈R, but (3,2)∉R(3,2) \notin R(3,2)∈/R ❌

    Since one pair fails symmetry, the relation is not symmetric.

    Therefore, C is true.

  5. Option D: Is RRR reflexive?

    A relation on A={1,2,3,4}A=\{1,2,3,4\}A={1,2,3,4} is reflexive if (1,1),(2,2),(3,3),(4,4)∈R.(1,1),(2,2),(3,3),(4,4) \in R.(1,1),(2,2),(3,3),(4,4)∈R.

    None of these ordered pairs are present in RRR.

    Hence, RRR is not reflexive.

    So, D is false.

  6. Final conclusion

    The only correct option is: C: not symmetric\boxed{\text{C: not symmetric}}C: not symmetric​

  7. Comparison with stored answer

    Stored correct answer: C

    Our derived answer is also C, so they agree.

Previous

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