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Relations and Functions (Class 12) · Question 22

JEE Main 2025 (Online) 7th April Morning ShiftNumericalHard📈 Topic in 45% papers+4
1

The number of relations on the set A = \1, 2, 3\, containing at most 6 elements including (1, 2), which are reflexive and transitive but not symmetric, is .

Answer

6

Solution

Reflexive (1, 1), (2, 2), (3, 3) R, and (1, 2) R. So at most 2 more pairs from \(2, 1), (1, 3), (3, 1), (2, 3), (3, 2)\.

No extra pair: R = (1, 1), (2, 2), (3, 3), (1, 2) is transitive and not symmetric ✓ → 1 relation

One extra pair:

(2, 1): symmetric ✗; (3, 1): needs (3, 2) ✗; (2, 3): needs (1, 3) ✗

(1, 3) ✓; (3, 2) ✓ → 2 relations

Two extra pairs (transitive closure must not need a fourth pair):

(1, 3), (2, 3) ✓ [(1, 2), (2, 3) (1, 3) present]

(1, 3), (3, 2) ✓ [(1, 3), (3, 2) (1, 2) present]

(3, 1), (3, 2) ✓ [(3, 1), (1, 2) (3, 2) present]

Every other pair fails: any set with (2, 1) forces a third pair; (1, 3), (3, 1) needs (3, 2); (3, 1), (2, 3) and (2, 3), (3, 2) need (1, 3). → 3 relations

All of these are not symmetric (they contain (1, 2) but not (2, 1)).

required number = 1 + 2 + 3 = 6

Answer: 6

JEE Main 2025 (Online) 7th April Morning Shift

Keep practising — Relations and Functions (Class 12)

2

Let f : R R be a continuous function satisfying f(0) = 1 and f(2x) - f(x) = x for all x R. If n \f(x) - f ( x2n ) \ = G(x), then r=110 G (r2 ) is equal to

  1. 215
  2. 420
  3. 385
  4. 540
JEE Main 2025 (Online) 4th April Morning Shift
3

Consider the sets A = \(x, y) R R : x2 + y2 = 25 \, B = \(x, y) R R : x2 + 9y2 = 144 \, C = \(x, y) Z Z : x2 + y2 4 \ and D = A B. The total number of one-one functions from the set D to the set C is:

  1. 15120
  2. 18290
  3. 17160
  4. 19320
JEE Main 2025 (Online) 4th April Morning Shift
4

Let f, g : (1, ) R be defined as f(x) = 2x + 35x + 2 and g(x) = 2 - 3x1 - x. If the range of the function f g : [2, 4] R is [ , ], then 1 - is equal to

  1. 56
  2. 2
  3. 29
  4. 68
JEE Main 2025 (Online) 4th April Morning Shift
5

Let A = \-3, -2, -1, 0, 1, 2, 3\ and R be a relation on A defined by xRy if and only if 2x - y \0, 1\. Let l be the number of elements in R. Let m and n be the minimum number of elements required to be added in R to make it reflexive and symmetric relations, respectively. Then l + m + n is equal to:

  1. 17
  2. 18
  3. 15
  4. 16
JEE Main 2025 (Online) 4th April Evening Shift
6

Let A = \-3, -2, -1, 0, 1, 2, 3\. Let R be a relation on A defined by x R y if and only if 0 x2 + 2y 4. Let l be the number of elements in R and m be the minimum number of elements required to be added in R to make it a reflexive relation. Then l + m is equal to

  1. 18
  2. 20
  3. 17
  4. 19
JEE Main 2025 (Online) 3rd April Morning Shift
7

Let f be a function such that f(x) + 3f ( 24x ) = 4x, x 0. Then f(3) + f(8) is equal to

  1. 13
  2. 11
  3. 10
  4. 12
JEE Main 2025 (Online) 3rd April Evening Shift
8

Let A = \-2, -1, 0, 1, 2, 3\. Let R be a relation on A defined by xRy if and only if y = \x, 1\. Let l be the number of elements in R. Let m and n be the minimum number of elements required to be added in R to make it reflexive and symmetric relations, respectively. Then l + m + n is equal to

  1. 11
  2. 12
  3. 14
  4. 13
JEE Main 2025 (Online) 3rd April Evening Shift
9

Let f : R R be a twice differentiable function such that ( x y)(f(2x + 2y) - f(2x - 2y)) = ( x y)(f(2x + 2y) + f(2x - 2y)), for all x, y R. If f'(0) = 12, then the value of 24f'' ( 5 3 ) is :

  1. 2
  2. 3
  3. -3
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JEE Main 2025 (Online) 2nd April Morning Shift
10

Let A be the set of all functions f : Z Z and R be a relation on A such that R = \(f, g) : f(0) = g(1) and f(1) = g(0)\. Then R is :

  1. Symmetric and transitive but not reflexive
  2. Symmetric but neither reflexive nor transitive
  3. Transitive but neither reflexive nor symmetric
  4. Reflexive but neither symmetric nor transitive
JEE Main 2025 (Online) 2nd April Morning Shift
11

Define a relation R on the interval [0, 2 ) by x R y if and only if 2 x - 2 y = 1. Then R is :

  1. both reflexive and symmetric but not transitive
  2. both reflexive and transitive but not symmetric
  3. reflexive but neither symmetric nor transitive
  4. an equivalence relation
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