JEE Main & Advanced JEE Main Paper (Held On 15 April 2018) Slot-I

  • question_answer
    Consider the following two binary relations on the set \[\text{A=}\left\{ \text{a,b,c} \right\}\text{:}{{\text{R}}_{\text{1}}}\text{=}\left\{ \left( \text{c,a} \right)\text{,}\left( \text{b,b} \right)\text{,}\left( \text{a,c} \right)\text{,}\left( \text{c,c} \right)\text{,}\left( \text{b,c} \right)\text{,}\left( \text{a,a} \right) \right\}\] and \[R2=\left\{ \left( a,b \right),\left( b,a \right),\left( c,c \right),\left( c,a \right),\left( a,a \right),\left( b,b \right),\left( a,c \right) \right\}\] Then                                                                                                                [JEE Online 15-04-2018]

    A) \[{{R}_{2}}\] is symmetric but it is not transitive

    B) Both \[{{R}_{1}}\] and \[{{R}_{2}}\] are transitive

    C) Both \[{{R}_{1}}\] and \[{{R}_{2}}\] are not symmetric

    D) \[{{R}_{1}}\] is not symmetric but it is transitive

    Correct Answer: A

    Solution :

    Both \[{{R}_{1}}\]and \[{{R}_{2}}\] are symmetric as for any \[({{a}_{1}},{{a}_{2}})\in {{R}_{1}}\], we have \[({{a}_{2}},{{a}_{1}})\in {{R}_{1}}\] and same thing can be verified for \[{{R}_{2}}\] as well \[({{a}_{1}}\ne {{a}_{2}})\]. For checking transitivity, we observe for \[{{R}_{2}}\] that, \[(b,a)\in {{R}_{2}},(a,c)\in {{R}_{2}}\] but \[(b,c){{R}_{2}}\]. Similarly, for \[{{R}_{1}},(b,c)\in {{R}_{1}},(c,a)\in {{R}_{1}}\], but \[(b,a){{R}_{1}}\]. So neither \[{{R}_{1}}\]nor \[{{R}_{2}}\] is transitive. So, the correct answer is option A.


You need to login to perform this action.
You will be redirected in 3 sec spinner