12th Class Mathematics Relations and Functions Question Bank Case Based (MCQs) - Relations and Functions

  • question_answer
    Directions : (6 - 10)
    Sherlin and Danju are playing Ludo at home during Covid-19. While rolling the dice, Sherlin's sister Raji observed and noted the possible outcomes of the throw every time belongs to set \[\left\{ 1,\text{ }2,\text{ }3,\text{ }4,\text{ }5,\text{ }6 \right\}\]. Let A be the set of players while B be the set of all possible outcomes.
    \[A=\left\{ S,\,D \right\},\,B=\left\{ 1,\,2,\,3,\,4,\,5,\,6 \right\}\]
    Let \[R\,\,:\,B\to B\] be defined by \[R=\left\{ \left( x,\,y \right) \right.:y\] is divisible by x} is

    A) Reflexive and transitive but not symmetric

    B) Reflexive and symmetric and not transitive

    C) Not reflexive but symmetric and transitive

    D) Equivalence

    Correct Answer: A

    Solution :

    \[R=\left\{ \left( 1,\,1 \right),\,\left( 1,\,2 \right),\,\left( 1,3 \right),\,\left( 1,4 \right)\,\left( 1,\,5 \right),\,\left( 1,6 \right) \right.\] \[\left. \left( 2,\,2 \right),\,\left( 2,\,4 \right),\,\left( 2,\,6 \right),\,\left( 3,\,3 \right),\,\left( 3,\,6 \right),\,\left( 4,\,4 \right),\left( 5,5 \right),\,\left( 6,\,6 \right) \right\}\] here \[\left( a,\,a \right)\in R\,\,\forall \,\,a\,\,\in \,B\] \[\therefore \] R is reflexive Also \[\left( 1,\,\,2 \right)\in R\] but \[\left( 2,\,\,1 \right)-\notin \,R\] \[\therefore \] R is not symmetric Clearly \[\left( a,\,b \right)\in R,\,\left( b,\,c \right)\in R\Rightarrow \left( a,\,c \right)\in R\] \[\forall \,a,\,b,\,c\,\in B\] \[\therefore \] R is transitive.


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