Question
Let the set of all relations R on the set \ a, b, c, d, e, f\ , such that R is reflexive and symmetric, and R contains exactly 10 elements, be denoted by S. Then the number of elements in S is ______
JEE Advanced
Mathematics
Sets and Relations
2025
JEE Advanced 2025 (Paper 1)
JEE Advanced Mathematics Question (2025) — Solution
Options
- A. A
- B. B
- C. C
- D. D
Answer
A. A
Step-by-step solution
For relation to be reflexive all the diagonal elements must be taken and out of remaining 30 elements there are 15 pairs and we need 2 pairs such that R contains exactly 10 elements and is both reflexive and symmetric. number of ways = ^ 15 C _2=105
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