JEE MAIN - Mathematics (2024 - 27th January Morning Shift - No. 3)
Let $S=\{1,2,3, \ldots, 10\}$. Suppose $M$ is the set of all the subsets of $S$, then the relation
$\mathrm{R}=\{(\mathrm{A}, \mathrm{B}): \mathrm{A} \cap \mathrm{B} \neq \phi ; \mathrm{A}, \mathrm{B} \in \mathrm{M}\}$ is :
$\mathrm{R}=\{(\mathrm{A}, \mathrm{B}): \mathrm{A} \cap \mathrm{B} \neq \phi ; \mathrm{A}, \mathrm{B} \in \mathrm{M}\}$ is :
symmetric only
reflexive only
symmetric and reflexive only
symmetric and transitive only
Explanation
Let $$S=\{1,2,3, \ldots, 10\}$$
$$R=\{(A, B): A \cap B \neq \phi ; A, B \in M\}$$
For Reflexive,
$$M$$ is subset of '$$S$$'
So $$\phi \in \mathrm{M}$$
for $$\phi \cap \phi=\phi$$
$$\Rightarrow$$ but relation is $$\mathrm{A} \cap \mathrm{B} \neq \phi$$
So it is not reflexive.
For symmetric,
$$\begin{array}{ll} \text { ARB } & \mathrm{A} \cap \mathrm{B} \neq \phi, \\ \Rightarrow \mathrm{BRA} & \Rightarrow \mathrm{B} \cap \mathrm{A} \neq \phi, \end{array}$$
So it is symmetric.
For transitive,
$$\begin{aligned} \text { If } A & =\{(1,2),(2,3)\} \\ B & =\{(2,3),(3,4)\} \\ C & =\{(3,4),(5,6)\} \end{aligned}$$
$$\mathrm{ARB}$$ & $$\mathrm{BRC}$$ but $$\mathrm{A}$$ does not relate to $$\mathrm{C}$$ So it not transitive
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