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Standalone Questions
#1015
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2024
JEE Main 2024 (Online) 8th April Evening Shift
KNOWLEDGE
4 Marks
Let $A = {2, 3, 6, 8, 9, 11}$ and $B = {1, 4, 5, 10, 15}$. Let $R$ be a relation on $A \times B$ defined by $(a, b)R(c, d)$ if and only if $3ad - 7bc$ is an even integer. Then the relation $R$ is
(A) reflexive but not symmetric.
(B) an equivalence relation.
(C) reflexive and symmetric but not transitive.
(D) transitive but not symmetric.
Key: C
Sol:
Sol:
Given that $(a, b)R(c, d) \Rightarrow 3ad - 7bc \in \text{even}$.
For reflexive, we need to check if $(a, b)R(a, b)$.
$(a, b)R(a, b) \Rightarrow 3ab - 7ba = -4ab \in \text{even}$. This is true since the product $ab$ will be an integer, and $-4$ times an integer is even.
Thus, $R$ is reflexive.
For symmetric, if $(a, b)R(c, d)$, then $(c, d)R(a, b)$ must also be true.
$(a, b)R(c, d) \Rightarrow 3ad - 7bc = 2m$ for some integer $m$.
$(c, d)R(a, b) \Rightarrow 3cb - 7ad$. We want to show this is even.
$3cb - 7ad = -7ad + 3cb = -(7ad - 3cb) = -(7ad - 3cb + 3ad - 3ad - 7bc + 7bc) = -(10ad - 10bc - (3ad - 7bc)) = -10(ad - bc) + (3ad-7bc)$
#1014
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 22nd January Morning Shift
KNOWLEDGE
4 Marks
The number of non-empty equivalence relations on the set ${1, 2, 3}$ is :
(A) $7$
(B) $4$
(C) $5$
(D) $6$
Key: C
Sol:
Sol:
An equivalence relation on a finite set is uniquely determined by its partition into equivalence classes. Counting the number of ways to partition the set ${1, 2, 3}$:
1. Three blocks: Each element in its own block. There is only one way: ${{1}, {2}, {3}}$.
2. Two blocks: We can have ${{1, 2}, {3}}$, ${{1, 3}, {2}}$, or ${{2, 3}, {1}}$. There are 3 ways.
3. One block: All elements together. There is only one way: ${{1, 2, 3}}$.
In total, there are $1 + 3 + 1 = 5$ distinct partitions, which means there are 5 equivalence relations on the set ${1, 2, 3}$.
#1013
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 22nd January Morning Shift
KNOWLEDGE
4 Marks
Let $A = {1, 2, 3, …, 10}$ and $B = {\frac{m}{n} : m, n \in A, m < n$ and $gcd(m, n) = 1}$. Then $n(B)$ is equal to :
(A) $29$
(B) $31$
(C) $37$
(D) $36$
Key: B
Sol:
Sol:
To find the number of elements in set $B$, we consider pairs $(\frac{m}{n})$ where $m, n \in A$ with $m < n$ and $gcd(m, n) = 1$.
Here's the breakdown for each possible $m$:
For $m = 1$:
Possible values for $n$ are $2, 3, 4, 5, 6, 7, 8, 9, 10$.
Total pairs: $9$.
For $m = 2$:
Possible values for $n$ are $3, 5, 7, 9$ (since these have $gcd(2, n) = 1$).
Total pairs: $4$.
For $m = 3$:
Possible values for $n$ are $4, 5, 7, 8, 10$.
Total pairs: $5$.
For $m = 4$:
Possible values for $n$ are $5, 7, 9$.
Total pairs: $3$.
For $m = 5$:
Possible values for $n$ are $6, 7, 8, 9$.
Total pairs: $4$.
For $m = 6$:
Possible value for $n$ is $7$.
Total pairs: $1$.
For $m = 7$:
Possible values for $n$ are $8, 9, 10$.
Total pairs: $3$.
For $m = 8$:
Possible value for $n$ is $9$.
Total pairs: $1$.
For $m = 9$:
Possible value for $n$ is $10$.
Total pairs: $1$.
Adding all these up, the total number of elements in set $B$ is:
$9 + 4 + 5 + 3 + 4 + 1 + 3 + 1 + 1 = 31$
#1012
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 23rd January Morning Shift
KNOWLEDGE
4 Marks
Let $R = \{(1, 2), (2, 3), (3, 3)\}$ be a relation defined on the set $\{1, 2, 3, 4\}$. Then the minimum number of elements, needed to be added in $R$ so that $R$ becomes an equivalence relation, is:
(A) 9
(B) 8
(C) 7
(D) 10
Key: C
Sol:
Sol:
For $R$ to be an equivalence relation on $A = \{1, 2, 3, 4\}$, it must be reflexive, symmetric and transitive.
1. **Reflexive:** $R$ must contain $(1, 1), (2, 2), (3, 3), (4, 4)$. Since $(3,3)$ is already in $R$, we need to add $(1, 1), (2, 2), (4, 4)$.
2. **Symmetric:** $R$ must contain $(2, 1)$ and $(3, 2)$ because it contains $(1, 2)$ and $(2, 3)$.
3. **Transitive:** Since $(1, 2)$ and $(2, 3)$ are in $R$, $(1, 3)$ must also be in $R$. And since we added $(3,2)$ now we must add $(1,2)$. Which already exists.
So, the minimum elements to be added are:
$(1, 1), (2, 2), (4, 4), (2, 1), (3, 2), (1, 3)$.
Therefore, the minimum number of elements to be added is $7$.
#1011
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 23rd January Evening Shift
KNOWLEDGE
4 Marks
Let $A = {(x, y) ∈ R × R : |x + y| ⩾ 3}$ and $B = {(x, y) ∈ R × R : |x| + |y| ≤ 3}$. If $C = {(x, y) ∈ A ∩ B : x = 0$ or $y = 0}$, then $\sum_{(x, y) ∈ C} |x + y|$ is :
(A) 18
(B) 24
(C) 15
(D) 12
Key: D
Sol:
Sol:
From the image, we can determine that the points in set C are $(3,0)$, $(-3,0)$, $(0,3)$ and $(0,-3)$.
Thus, $C = {(3, 0), (-3, 0), (0, 3), (0, -3)}$.
$\sum |x + y| = |3 + 0| + |-3 + 0| + |0 + 3| + |0 + (-3)| = 3 + 3 + 3 + 3 = 12$.
#1010
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 23rd January Evening Shift
KNOWLEDGE
4 Marks
Let $X = R \times R$. Define a relation R on X as: $(a_1, b_1) R (a_2, b_2) \Leftrightarrow b_1 = b_2$ Statement I: $R$ is an equivalence relation. Statement II: For some $(a, b) \in X$, the set $S = \{(x, y) \in X : (x, y)R(a, b)\}$ represents a line parallel to $y = x$. In the light of the above statements, choose the correct answer from the options given below:
(A) Both Statement I and Statement II are true
(B) Statement I is true but Statement II is false
(C) Both Statement I and Statement II are false
(D) Statement I is false but Statement II is true
Key: B
Sol:
Sol:
Statement I: Reflexive: $(a_1, b_1) R (a_1, b_1) \Rightarrow b_1 = b_1$ (True). Symmetric: $(a_1, b_1) R (a_2, b_2) \Rightarrow b_1 = b_2$ and $(a_2, b_2) R (a_1, b_1) \Rightarrow b_2 = b_1$ (True). Transitive: $(a_1, b_1) R (a_2, b_2) \Rightarrow b_1 = b_2$ and $(a_2, b_2) R (a_3, b_3) \Rightarrow b_2 = b_3$. Thus, $b_1 = b_3$, so $(a_1, b_1) R (a_3, b_3)$ (True). Hence, relation $R$ is an equivalence relation, and Statement I is true. For Statement II: $(x, y) R (a, b) \Rightarrow y = b$. This represents a line $y=b$, which is parallel to the x-axis. It is not parallel to the line $y=x$. Therefore, Statement II is false.
#1009
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 24th January Evening Shift
KNOWLEDGE
4 Marks
Let $A = {x \in (0, \pi) - {\frac{\pi}{2}} : \log_{(2/\pi)} |\sin x| + \log_{(2/\pi)} |\cos x| = 2}$ and $B = {x \ge 0 : x(x-4) - 3|x-2| + 6 = 0}$. Then $n(A \cup B)$ is equal to :
(A) 4
(B) 8
(C) 6
(D) 2
Key: B
Sol:
Sol:
For set A: $\log_{\frac{2}{\pi}} |\sin x| + \log_{\frac{2}{\pi}} |\cos x| = 2$ $\Rightarrow \log_{\frac{2}{\pi}} |\sin x \cdot \cos x| = 2$ $\Rightarrow |\sin x \cos x| = (\frac{2}{\pi})^2$ $\Rightarrow |\frac{1}{2} \sin 2x| = \frac{4}{\pi^2}$ $\Rightarrow |\sin 2x| = \frac{8}{\pi^2}$ Since $0 < \frac{8}{\pi^2} < 1$, there are 4 solutions for $x \in (0, \pi)$. For set B: Case 1: $x < 2$, $x(x-4) + 3(x-2) + 6 = 0$ $\Rightarrow x^2 - 4x + 3x - 6 + 6 = 0$ $\Rightarrow x^2 - x = 0$ $\Rightarrow x(x-1) = 0$, so $x = 0, 1$. Case 2: $x > 2$, $x(x-4) - 3(x-2) + 6 = 0$ $\Rightarrow x^2 - 4x - 3x + 6 + 6 = 0$ $\Rightarrow x^2 - 7x + 12 = 0$ $\Rightarrow (x-3)(x-4) = 0$, so $x = 3, 4$. Thus, $B = {0, 1, 3, 4}$, so $n(B) = 4$. Since $A$ and $B$ are disjoint, $n(A \cup B) = n(A) + n(B) = 4 + 4 = 8$.
#1008
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 28th January Morning Shift
KNOWLEDGE
4 Marks
The relation $R = {(x, y) : x, y ∈ Z$ and $x + y$ is even $}$ is:
(A) reflexive and transitive but not symmetric
(B) reflexive and symmetric but not transitive
(C) an equivalence relation
(D) symmetric and transitive but not reflexive
Key: C
Sol:
Sol:
The given relation is $R = {(x, y) : x, y ∈ Z$ and $x + y$ is even $}$.
Reflexive: For any $x ∈ Z$, $x + x = 2x$, which is even. So, $(x, x) ∈ R$. Thus, $R$ is reflexive.
Symmetric: If $(x, y) ∈ R$, then $x + y$ is even. Since $x + y = y + x$, $y + x$ is also even. So, $(y, x) ∈ R$. Thus, $R$ is symmetric.
Transitive: If $(x, y) ∈ R$ and $(y, z) ∈ R$, then $x + y$ is even and $y + z$ is even. Then $(x + y) + (y + z) = x + 2y + z$ is even. Since $2y$ is even, it follows that $x + z$ is even. So, $(x, z) ∈ R$. Thus, $R$ is transitive.
Since $R$ is reflexive, symmetric, and transitive, it is an equivalence relation.
#1007
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 29th January Morning Shift
KNOWLEDGE
4 Marks
Define a relation R on the interval $[0, π/2)$ by $x$ R $y$ if and only if $\sec^2x - \tan^2y = 1$. Then R is :
(A) both reflexive and symmetric but not transitive
(B) both reflexive and transitive but not symmetric
(C) reflexive but neither symmetric not transitive
(D) an equivalence relation
Key: D
Sol:
Sol:
To check if the relation R is reflexive, symmetric, and transitive:
1. **Reflexive:**
Replace $y$ with $x$ in the given relation: $\sec^2x - \tan^2x = 1$. This is a trigonometric identity, so the relation is reflexive.
2. **Symmetric:**
Given $\sec^2x - \tan^2y = 1$, we can rewrite this as $1 + \tan^2x - \tan^2y = 1$, which implies $\tan^2x = \tan^2y$. Also, $\sec^2x - \tan^2y = 1$ can be rewritten as $1 + \tan^2x - \sec^2y + 1 = 1$, leading to $\sec^2y - \tan^2x = 1$. Thus, if $xRy$, then $yRx$, so the relation is symmetric.
3. **Transitive:**
Suppose $\sec^2x - \tan^2y = 1$ and $\sec^2y - \tan^2z = 1$. Adding these two equations, we get:
$\sec^2x - \tan^2y + \sec^2y - \tan^2z = 1 + 1$
$\sec^2x + (\sec^2y - \tan^2y) - \tan^2z = 2$
Since $\sec^2y - \tan^2y = 1$, we have:
$\sec^2x + 1 - \tan^2z = 2$
$\sec^2x - \tan^2z = 1$
Thus, if $xRy$ and $yRz$, then $xRz$, so the relation is transitive.
Since the relation is reflexive, symmetric, and transitive, it is an equivalence relation.
#1006
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 29th January Evening Shift
KNOWLEDGE
4 Marks
Let $S = \mathbb{N} \cup \{0\}$. Define a relation R from S to $\mathbb{R}$ by: $R = \{(x, y) : \log_e y = x \log_e (\frac{2}{5}), x \in S, y \in \mathbb{R}\}$. Then, the sum of all the elements in the range of $R$ is equal to:
(A) $\frac{3}{2}$
(B) $\frac{10}{9}$
(C) $\frac{5}{2}$
(D) $\frac{5}{3}$
Key: D
Sol:
Sol:
Given $S = \{0, 1, 2, 3, ...\}$. Also, $\log_e y = x \log_e (\frac{2}{5})$.
This implies $y = (\frac{2}{5})^x$.
Since $x \in S$, $x$ can take values $0, 1, 2, 3, ...$.
The required sum is $1 + (\frac{2}{5})^1 + (\frac{2}{5})^2 + (\frac{2}{5})^3 + ... = \frac{1}{1 - \frac{2}{5}} = \frac{1}{\frac{3}{5}} = \frac{5}{3}$.
#1005
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
MEDIUM
2025
JEE Main 2025 (Online) 2nd April Morning Shift
Competency
4 Marks
Let $A$ be the set of all functions $f: Z \rightarrow Z$ and $R$ be a relation on $A$ such that $R = {(f, g): f(0) = g(1) \text{ and } f(1) = g(0)}$. Then $R$ is :
(A) Symmetric and transitive but not reflective
(B) Symmetric but neither reflective nor transitive
(C) Transitive but neither reflexive nor symmetric
(D) Reflexive but neither symmetric nor transitive
Key: B
Sol:
Sol:
To determine if the relation $R$ is reflexive, symmetric, and transitive, we analyze each property separately.
Reflexive: For $R$ to be reflexive, $(f, f)$ must be in $R$. This means $f(0) = f(1)$ and $f(1) = f(0)$ must be true for all $f$. However, $f(0)$ is not necessarily equal to $f(1)$ for all functions $f$. Therefore, $R$ is not reflexive.
Symmetric: If $(f, g) \in R$, then $f(0) = g(1)$ and $f(1) = g(0)$. To check for symmetry, we need to verify if $(g, f) \in R$. If $f(0) = g(1)$, then $g(1) = f(0)$. And if $f(1) = g(0)$, then $g(0) = f(1)$. This shows that if $(f, g) \in R$, then $(g, f) \in R$, so $R$ is symmetric.
Transitive: If $(f, g) \in R$ and $(g, h) \in R$, then $f(0) = g(1)$, $f(1) = g(0)$, $g(0) = h(1)$, and $g(1) = h(0)$. For $R$ to be transitive, we need to check if $(f, h) \in R$, which means $f(0) = h(1)$ and $f(1) = h(0)$. We have $f(0) = g(1) = h(0)$, so $f(0) = h(0)$. Also, $f(1) = g(0) = h(1)$, so $f(1) = h(1)$. Therefore, $f(0) = g(1)$ and $g(1) = h(0)$ implies $f(0) = h(0)$ and $f(1) = g(0)$ and $g(0) = h(1)$ implies $f(1) = h(1)$. Since $f(0)$ is not necessarily equal to $h(1)$ and $f(1)$ is not necessarily equal to $h(0)$, $R$ is not transitive. Actually $f(0) = h(0)$ and $f(1) = h(1)$ so this doesn't imply that $f(0) = h(1)$ and $f(1) = h(0)$ so the relation is not transitive
Therefore, the relation $R$ is symmetric but neither reflexive nor transitive.
#1004
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
MEDIUM
2025
JEE Main 2025 (Online) 2nd April Evening Shift
Competency
4 Marks
Let $A = {1, 2, 3, ..., 100}$ and $R$ be a relation on $A$ such that $R = {(a, b) : a = 2b + 1}$. Let $(a_1, a_2), (a_2, a_3), (a_3, a_4), ..., (a_k, a_{k+1})$ be a sequence of $k$ elements of $R$ such that the second entry of an ordered pair is equal to the first entry of the next ordered pair. Then the largest integer k , for which such a sequence exists, is equal to :
(A) 6
(B) 8
(C) 7
(D) 5
Key: A
Sol:
Sol:
The relation $R$ is defined on the set $A = {1, 2, 3, ..., 100}$ such that $R = {(a, b) : a = 2b + 1}$. We need to find the largest integer $k$ for which there exists a sequence of $k$ ordered pairs from $R$ where the second element of each pair is the first element of the next pair.
The sequence in terms of $k$ is: $(a_1, a_2), (a_2, a_3), ..., (a_k, a_{k+1})$. Here, each $a_i$ satisfies the equation $a_i = 2a_{i+1} + 1$. Consequently, $a_1 = 2a_2 + 1$, making $a_1$ an odd number.
Let's examine the pattern:
$a_2 = 2a_3 + 1$, implying $a_1 = 2(2a_3 + 1) + 1 = 4a_3 + 3$.
$a_3 = 2a_4 + 1$, leading to $a_1 = 4(2a_4 + 1) + 3 = 8a_4 + 7$.
Continuing this pattern, we find:
$a_k = 2a_{k+1} + 1 \implies a_1 = 2^k \cdot a_{k+1} + (2^k - 1)$ where $a_{k+1}$ needs to be in set $A$. This implies:
$a_{k+1} = \frac{a_1 + 1 - 2^k}{2^k}$
Thus, $2^k \mid (a_1 + 1)$. The task is to find the highest $k$ where $2^k$ divides any $e_i$ in ${2, ..., 101}$.
The largest power of 2 that divides an element within this range determines $k$.
After computation, we find that $k$ can be a maximum of 6 because $2^6 = 64$ divides $95+1 = 96$, but $2^7 = 128$ does not divide any $e_i$ for $e_i \in A$. Therefore, the maximum $k$ is 6.
The sequence corresponding to this maximum $k$ is: $(95, 47), (47, 23), (23, 11), (11, 5), (5, 2)$
#1003
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 3rd April Morning Shift
KNOWLEDGE
4 Marks
Let $A = {-3, -2, -1, 0, 1, 2, 3}$. Let R be a relation on A defined by $xRy$ if and only if $0 \le x^2 + 2y \le 4$. 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
(A) 18
(B) 20
(C) 17
(D) 19
Key: A
Sol:
Sol:
First, we determine the pairs $(x, y)$ that satisfy the condition $0 \le x^2 + 2y \le 4$ for the given set $A = \{-3, -2, -1, 0, 1, 2, 3\}$.
For $y = -3$, $x^2 + 2(-3) \le 4 \implies x^2 \le 10$, so $x$ can be $-3$ or $3$.
For $y = -2$, $x^2 + 2(-2) \le 4 \implies x^2 \le 8$, so $x$ can be $-2$ or $2$.
For $y = -1$, $x^2 + 2(-1) \le 4 \implies x^2 \le 6$, so $x$ can be $-2$ or $2$.
For $y = 0$, $x^2 + 2(0) \le 4 \implies x^2 \le 4$, so $x$ can be $-2, -1, 0, 1, 2$.
For $y = 1$, $x^2 + 2(1) \le 4 \implies x^2 \le 2$, so $x$ can be $-1, 0, 1$.
For $y = 2$, $x^2 + 2(2) \le 4 \implies x^2 \le 0$, so $x$ can only be $0$.
Thus, the relation R consists of the following pairs:
$R = \{(3, -3), (-3, -3), (-2, -2), (2, -2), (-2, -1), (2, -1), (-2, 0), (-1, 0), (0, 0), (1, 0), (2, 0), (-1, 1), (0, 1), (1, 1), (0, 2)\}$.
The number of elements in R is $l = 15$.
To make R reflexive, it must include all pairs $(x, x)$ for every $x \in A$. The set A has 7 elements, so the reflexive relation must contain $(-3, -3), (-2, -2), (-1, -1), (0, 0), (1, 1), (2, 2), (3, 3)$. Currently, R has $(-3,-3), (-2, -2), (0,0), (1,1)$. So the missing pairs are $(-1, -1), (2, 2), (3, 3)$, meaning $m = 3$.
Therefore, $l + m = 15 + 3 = 18$.
#1002
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
HARD
2025
JEE Main 2025 (Online) 3rd April Evening Shift
Competency
4 Marks
Let $A = \{-2, -1, 0, 1, 2, 3\}$. Let R be a relation on $A$ defined by $xRy$ if and only if $y = \max\{x, 1\}$. 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
(A) 11
(B) 12
(C) 14
(D) 13
Key: B
Sol:
Sol:
The relation $R$ is defined such that $y = \max(x, 1)$. Therefore, we find the following pairs:
$x = -2 \implies y = \max(-2, 1) = 1$, so $(-2, 1) \in R$.
$x = -1 \implies y = \max(-1, 1) = 1$, so $(-1, 1) \in R$.
$x = 0 \implies y = \max(0, 1) = 1$, so $(0, 1) \in R$.
$x = 1 \implies y = \max(1, 1) = 1$, so $(1, 1) \in R$.
$x = 2 \implies y = \max(2, 1) = 2$, so $(2, 2) \in R$.
$x = 3 \implies y = \max(3, 1) = 3$, so $(3, 3) \in R$.
Thus, $R = \{(-2, 1), (-1, 1), (0, 1), (1, 1), (2, 2), (3, 3)\}$, and $l = 6$.
To make $R$ reflexive, we need to add $(-2, -2), (-1, -1), (0, 0)$. Thus, $m = 3$.
To make $R$ symmetric, we need to add $(1, -2), (1, -1), (1, 0)$. Thus, $n = 3$.
Therefore, $l + m + n = 6 + 3 + 3 = 12$.
#1001
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 4th April Morning Shift
KNOWLEDGE
4 Marks
Consider the sets $A = \{(x, y) \in R \times R : x^2 + y^2 = 25\}$, $B = \{(x, y) \in R \times R : x^2 + 9y^2 = 144\}$, $C = \{(x, y) \in Z \times Z : x^2 + y^2 \le 4\}$ and $D = A \cap B$. The total number of one-one functions from the set $D$ to the set $C$ is:
(A) $15120$
(B) $18290$
(C) $17160$
(D) $19320$
Key: C
Sol:
Sol:
The given sets are $A = \{(x, y) \in R \times R : x^2 + y^2 = 25\}$ and $B = \{(x, y) \in R \times R : x^2 + 9y^2 = 144\}$. To find the intersection of A and B, we solve the system of equations. Subtracting the equation for A from the equation for B gives: $x^2 + 9y^2 - (x^2 + y^2) = 144 - 25$, which simplifies to $8y^2 = 119$, so $y^2 = \frac{119}{8}$. Substituting this into the equation for A, we get $x^2 = 25 - \frac{119}{8} = \frac{200 - 119}{8} = \frac{81}{8}$. Thus, $x = \pm \frac{9}{\sqrt{8}}$ and $y = \pm \frac{\sqrt{119}}{\sqrt{8}}$. Since $D = A \cap B$, the set D contains 4 points. Now, consider the set $C = \{(x, y) \in Z \times Z : x^2 + y^2 \le 4\}$. The integer pairs (x, y) that satisfy this condition are: $(\pm 2, 0)$, $(0, \pm 2)$, $(\pm 1, 0)$, $(0, \pm 1)$, $(\pm 1, \pm 1)$, and $(0, 0)$. Counting these points, we find that there are 13 such pairs. The number of one-to-one functions from D to C is the number of ways to choose 4 elements from C and arrange them, which is $P(13, 4) = \frac{13!}{(13-4)!} = \frac{13!}{9!} = 13 \times 12 \times 11 \times 10 = 17160$.
#999
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 7th April Evening Shift
KNOWLEDGE
4 Marks
Let $A = \{ (\alpha, \beta) \in R \times R : |\alpha - 1| \leq 4 \text{ and } |\beta - 5| \leq 6 \}$ and $B = \{ (\alpha, \beta) \in R \times R : 16(\alpha - 2)^2 + 9(\beta - 6)^2 \leq 144 \}$. Then
(A) $A \subset B$
(B) $B \subset A$
(C) neither $A \subset B$ nor $B \subset A$
(D) $A \cup B = \{ (x, y) : -4 \leqslant x \leqslant 4, -1 \leqslant y \leqslant 11 \}$
Key: B
Sol:
Sol:
For set A, we have $|x - 1| \leq 4$ and $|y - 5| \leq 6$. This implies $-4 \leq x - 1 \leq 4$ and $-6 \leq y - 5 \leq 6$. Therefore, $-3 \leq x \leq 5$ and $-1 \leq y \leq 11$. For set B, we have $16(x - 2)^2 + 9(y - 6)^2 \leq 144$, which simplifies to $\frac{(x - 2)^2}{9} + \frac{(y - 6)^2}{16} \leq 1$. This represents an ellipse centered at $(2, 6)$ with semi-major axis 4 and semi-minor axis 3. From the diagram, it's clear that $B \subset A$.
#998
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 8th April Evening Shift
KNOWLEDGE
4 Marks
Let $A = {0, 1, 2, 3, 4, 5}$. Let $R$ be a relation on $A$ defined by $(x, y) \in R$ if and only if $\max{x, y} \in {3, 4}$. Then among the statements
(S1): The number of elements in $R$ is $18$, and
(S2): The relation $R$ is symmetric but neither reflexive nor transitive
(S1): The number of elements in $R$ is $18$, and
(S2): The relation $R$ is symmetric but neither reflexive nor transitive
(A) both are false
(B) only (S1) is true
(C) only (S2) is true
(D) both are true
Key: C
Sol:
Sol:
To determine the elements in the relation $R$, we need to find all pairs $(x, y)$ such that $\max(x, y) \in {3, 4}$. The set $A = {0, 1, 2, 3, 4, 5}$.
If $\max(x, y) = 3$, the pairs are $(0, 3), (1, 3), (2, 3), (3, 3), (3, 0), (3, 1), (3, 2)$.
If $\max(x, y) = 4$, the pairs are $(0, 4), (1, 4), (2, 4), (3, 4), (4, 4), (4, 0), (4, 1), (4, 2), (4, 3)$.
Thus, the total number of elements in $R$ is $7 + 9 = 16$. Therefore, statement S1 is false.
For statement S2, we check the properties of $R$:
Reflexivity: $(0, 0)$ is not in $R$, so $R$ is not reflexive.
Symmetry: If $(x, y) \in R$, then $\max(x, y) \in {3, 4}$, which implies $\max(y, x) \in {3, 4}$, so $(y, x) \in R$. Thus, $R$ is symmetric.
Transitivity: $(0, 3) \in R$ and $(3, 1) \in R$, but $(0, 1)$ is not in $R$. Therefore, $R$ is not transitive.
Statement S2 is true since $R$ is symmetric but neither reflexive nor transitive.
#997
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
UNDERSTAND
HARD
2025
JEE Main 2025 (Online) 4th April Morning Shift
Competency
4 Marks
Consider the sets $A = \{(x, y) \in R \times R : x^2 + y^2 = 25\}$, $B = \{(x, y) \in R \times R: x^2 + 9y^2 = 144\}$, $C = \{(x, y) \in Z \times Z: x^2 + y^2 \leq 4\}$ and $D = A \cap B$. The total number of one-one functions from the set $D$ to the set $C$ is:
(A) 15120
(B) 18290
(C) 17160
(D) 19320
Key: C
Sol:
Sol:
$A = \{(x, y) \in R \times R : x^2 + y^2 = 25\}$, $B = \{(x, y) \in R \times R: x^2 + 9y^2 = 144\}$
$x^2 + 9y^2 - (x^2 + y^2) = 144 - 25$
Plug in $y^2 = \frac{119}{8}$ into either equation to find $x$.
$x^2 = 25 - \frac{119}{8}$
$x^2 = \frac{200 - 119}{8}$
$x^2 = \frac{81}{8}$
$x = \pm \sqrt{\frac{81}{8}}$, $y = \pm \sqrt{\frac{119}{8}}$
Now, $C = \{(x, y) \in Z \times Z: x^2 + y^2 \leq 4\}$
Valid points are $(-2, 0), (-1, -1), (-1, 0), (-1, 1), (0, -2), (0, -1), (0, 0), (0, 1), (0, 2), (1, -1), (1, 0), (1, 1)$
$\therefore$ Total valid points in $C = 13$
$\Rightarrow$ There are 4 distinct real points in set $D$
$\therefore$ The number of one-one functions from $D$ to $C$
$\Rightarrow {}^{13}P_4 \Rightarrow \frac{13!}{(13-4)!} = \frac{13!}{9!} = 17160$
#996
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 4th April Evening Shift
KNOWLEDGE
4 Marks
Let $A = \{-3, -2, -1, 0, 1, 2, 3\}$ and R be a relation on A defined by $xRy$ if and only if $2x - y \in \{0, 1\}$. 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:
(A) 17
(B) 18
(C) 15
(D) 16
Key: A
Sol:
Sol:
$xRy \Leftrightarrow 2x - y \in \{0, 1\}$
$\Rightarrow y = 2x$ or $y = 2x - 1$
$A=\{-3,-2,-1, 0, 1, 2, 3\}$
$R = \{(-1,-2), (0,0), (1, 2), (-1, -3), (0, -1), (1, 1), (2,3)\}$
$\Rightarrow I=7$
For $R$ to be reflexive $(0,0), (1,1) \in R$
But other $(a, a)$ such that $2a - a \in \{0, 1\}$
$\Rightarrow a \in \{0, 1\}$
5 other pairs needs to be added
$\Rightarrow m=5$
$xRy \Rightarrow yRx$ to be symmetric
$(-1, -2) \Rightarrow (-2, -1)$
$(1, 2) \Rightarrow (2, 1)$
$(-1, -3) \Rightarrow (-3, -1)$
$(0, -1) \Rightarrow (-1, 0)$
$(2, 3) \Rightarrow (3, 2)$
$\Rightarrow 5$ needs to be added, $n=5$
$\Rightarrow l+m+n=17$
#995
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2025
JEE Main 2025 (Online) 7th April Evening Shift
KNOWLEDGE
4 Marks
Let $A = { (\alpha, \beta ) \in R \times R : |\alpha - 1| \leq 4$ and $|\beta - 5| \leq 6 }$
and $B = { (\alpha, \beta ) \in R \times R : 16(\alpha - 2)^{2}+ 9(\beta - 6)^{2} \leq 144 }$.
Then
and $B = { (\alpha, \beta ) \in R \times R : 16(\alpha - 2)^{2}+ 9(\beta - 6)^{2} \leq 144 }$.
Then
(A) A $A \subset B$
(B) B $B \subset A$
(C) C neither $A \subset B$ nor $B \subset A$
(D) D $A \cup B = { (x, y) : -4 \leqslant x \leqslant 4, -1 \leqslant y \leqslant 11 }$
Key: B
Sol:
Sol:
$A: |x-1| \leq 4$ and $|y-5| \leq 6$
$\Rightarrow -4 \leq x-1 \leq 4 \Rightarrow -6 \leq y-5 \leq 6$
$\Rightarrow -3 \leq x \leq 5 \Rightarrow -1 \leq y \leq 11$
$B : 16(x-2)^{2} + 9(y-6)^{2} \leq 144$
$B : \frac{(x-2)^{2}}{9} + \frac{(y-6)^{2}}{16} \leq 1$
From Diagram $B \subset A$