Before You Begin
Question #41104
The Question
Let be the set of all matrices over with entries from . We define three subsets of as follows: where denotes the matrix obtained by swapping the first and second rows of , and is the null matrix. Let . Let be the number of reflexive relations on , and be the number of symmetric relations on . Find the value of .
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 .
Furthermore, even if they correctly deduce , 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
| Subject | Mathematics |
| Chapter | Relations and Functions - Class 12 |
| Concept | Reflexivity in Empty Sets |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |