Class CBSE Class 12 Mathematics Relations and Functions Q #789
KNOWLEDGE BASED
UNDERSTAND
1 Marks 2023 MCQ SINGLE
Let A={3,5}. Then number of reflexive relations on A is
(A) 2
(B) 4
(C) 0
(D) 8
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Step-by-Step Solution

Let A = {3, 5}. A relation R on A is reflexive if (a, a) ∈ R for all a ∈ A.

In this case, for R to be reflexive, (3, 3) and (5, 5) must be in R.

The possible elements in a relation on A are: (3, 3), (3, 5), (5, 3), (5, 5).

Since (3, 3) and (5, 5) must be in R, we only need to consider whether (3, 5) and (5, 3) are in R or not.

We have the following possibilities:

  1. R1 = {(3, 3), (5, 5)}
  2. R2 = {(3, 3), (5, 5), (3, 5)}
  3. R3 = {(3, 3), (5, 5), (5, 3)}
  4. R4 = {(3, 3), (5, 5), (3, 5), (5, 3)}

Therefore, there are 4 reflexive relations on A.

Correct Answer: 4

AI Suggestion: Option B

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Pedagogical Audit
Bloom's Analysis: This is an UNDERSTAND question because it requires the student to comprehend the definition of a reflexive relation and apply it to a given set.
Knowledge Dimension: CONCEPTUAL
Justification: The question tests the understanding of the concept of reflexive relations, rather than recalling facts or performing a specific procedure.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly assesses the understanding of definitions and concepts related to relations and functions as covered in the textbook.

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