CUET · MATHS · PYQ PAPER 2025

If R and S are two equivalence relations on a set A, then

A \(R \cup S\) is also an equivalence relation.
B \((R \cup S)^{-1}\) is also an equivalence relation.
C \((R \cap S)^{-1}\) is also an equivalence relation.
D \(R \cap S\) is not an equivalence relation.

Verified Solution

Answer & Solution

Correct Answer

(C) \((R \cap S)^{-1}\) is also an equivalence relation.

Step-by-step Solution

Detailed explanation

\(R \cap S\) is an equivalence relation. The inverse of an equivalence relation is an equivalence relation. Therefore, \((R \cap S)^{-1}\) is also an equivalence relation.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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