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Question #41104

Difficulty: 8/10 | 🟢 Free

The Question

Let SS be the set of all 3×33 \times 3 matrices over R\mathbb{R} with entries from {0,1}\{0, 1\}. We define three subsets of SS as follows: X={A∈S∣det⁡(A)=0 and det⁡(R12(A))≠0}X = \{ A \in S \mid \det(A) = 0 \text{ and } \det(R_{12}(A)) \neq 0 \} Y={A∈S∣det⁡(A)≠0 and det⁡(R12(A))=det⁡(A)}Y = \{ A \in S \mid \det(A) \neq 0 \text{ and } \det(R_{12}(A)) = \det(A) \} W={A∈S∣AT=−A and A≠O}W = \{ A \in S \mid A^T = -A \text{ and } A \neq O \} where R12(A)R_{12}(A) denotes the matrix obtained by swapping the first and second rows of AA, and OO is the 3×33 \times 3 null matrix. Let Z=X∪Y∪WZ = X \cup Y \cup W. Let nn be the number of reflexive relations on ZZ, and mm be the number of symmetric relations on ZZ. Find the value of n+mn + m.

Options

  • A.

    0

  • B.

    2

  • C.

    3

  • D.

    12

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Specialist

Targeted practice for niche, high-difficulty concepts that frequently appear in JEE Advanced exams.

Concepts Behind This Question

Reflexivity in Empty Sets|Singular vs Non-Singular Matrices|Row/Column Exchange Parity

Why This Question Is Tricky

Common Mistakes

This question tests the properties of determinants under elementary row operations and the formal definitions of relations on empty sets.

The 'Lethal Collision' occurs because students often assume that a set defined by complex matrix conditions must be non-empty, leading them to miscalculate ∣Z∣|Z|.

Furthermore, even if they correctly deduce Z=∅Z = \emptyset, they fall into the classic trap of assuming 0 reflexive and symmetric relations exist on an empty set.

By definition, the empty relation is vacuously reflexive and symmetric on the empty set, yielding exactly 1 relation of each type.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterRelations and Functions - Class 12
ConceptReflexivity in Empty Sets
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree