12th Class Mathematics Relations and Functions Question Bank Assertion And Reason (MCQs) - Relations and Functions

  • question_answer
    Assertion: A relation \[R=\left\{ \left( a,\,b \right)\,:\,\,|a-b|\,<\,2 \right\}\]defined on the set \[A=\left\{ 1,\,2,\,3,\,4,\,5 \right\}\] is reflexive.
    Reason: A relation R on the set A is said to be reflexive if for \[\left( a,\,b \right)\in \,R\] and\[\left( b,\,c \right)\in \,R\], we have \[\left( a,\,c \right)\in R\].
     

    A) Both A and R are individually true and R is the correct explanation of A.

    B) Both A and R are individually true and R is not the correct explanation of A.

    C) 'A' is true but 'R' is false

    D) 'A' is false but 'R' is true

    E) Both A and R are false.

    Correct Answer: C

    Solution :

    Given \[R=\left\{ \left( a,\,b \right)\,\,:\,\,|\,a\,-\,b|\,<\,2 \right\}\] = {(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (1, 2), (2, 1), (2, 3), (3, 2), (3, 4). (4, 3), (4, 5), (5, 4)}. Here \[\left( 1,\,1 \right)\in R\], \[\left( 2,\,\,2 \right)\in \,R\], \[\left( 3,\,\,3 \right)\,\in \,R\], \[\left( 4,\,\,4 \right)\in \,R\], \[\left( 5,\,5 \right)\in R\] \[\Rightarrow \]Relation R is reflexive on set \[A=\left\{ 1,\,2,\,3,\,4,\,5 \right\}\]\[\therefore \]Assertion A is true We know that relation R is reflexive if \[\left( a,\,a \right)\in R\,\,\forall \,a\in A\] \[\therefore \]Given Reason R is false Hence option [C] is the correct answer.


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