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Standalone Questions
#1079
Mathematics
Sets, Relations, and Functions
NUMERICAL
REMEMBER
EASY
2025
JEE Main 2025 (Online) 7th April Morning Shift
Competency
4 Marks
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 __________.
Key:
Sol:
Sol:
#1078
Mathematics
Sets, Relations, and Functions
NUMERICAL
APPLY
KNOWLEDGE
1 Marks
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 ________.
Key:
Sol:
Sol:
#1077
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2004
AIEEE
KNOWLEDGE
4 Marks
Let $R = \{(1, 3), (4, 2), (2, 4), (2, 3), (3, 1)\}$ be a relation on the set $A = \{1, 2, 3, 4\}$. The relation $R$ is:
(A) a function
(B) transitive
(C) not symmetric
(D) reflexive
Key: C
Sol:
Sol:
To determine if the relation $R$ is symmetric, we need to check if for every $(x, y)$ in $R$, the pair $(y, x)$ is also in $R$.
$R = \{(1, 3), (4, 2), (2, 4), (2, 3), (3, 1)\}$.
We have $(1, 3)$ in $R$, and $(3, 1)$ is also in $R$.
We have $(4, 2)$ in $R$, but $(2, 4)$ is also in $R$.
However, we have $(2, 3)$ in $R$, but $(3, 2)$ is not in $R$.
Since there exists a pair $(2, 3)$ in $R$ such that $(3, 2)$ is not in $R$, the relation $R$ is not symmetric.
Therefore, the correct answer is Option C: $R$ is not symmetric.
#1076
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2005
AIEEE
KNOWLEDGE
4 Marks
Let $R = \{(3, 3), (6, 6), (9, 9), (12, 12), (6, 12), (3, 9), (3, 12), (3, 6)\}$ be a relation on the set $A = \{3, 6, 9, 12\}$. The relation is :
(A) reflexive and symmetric only
(B) an equivalence relation
(C) reflexive only
(D) reflexive and transitive only
Key: D
Sol:
Sol:
To determine the properties of the relation $R$, we need to check for reflexivity, symmetry, and transitivity.
Reflexivity: A relation is reflexive if $(a, a) \in R$ for all $a \in A$. Since $(3, 3), (6, 6), (9, 9),$ and $(12, 12)$ are all in $R$, the relation is reflexive.
Symmetry: A relation is symmetric if whenever $(a, b) \in R$, then $(b, a) \in R$. We have $(6, 12) \in R$, but $(12, 6) \notin R$. Thus, the relation is not symmetric.
Transitivity: A relation is transitive if whenever $(a, b) \in R$ and $(b, c) \in R$, then $(a, c) \in R$. We have $(3, 6) \in R$ and $(6, 12) \in R$, and $(3, 12) \in R$. Also, $(3, 6) \in R$ and $(6, 6) \in R$, and $(3, 6) \in R$. The relation appears to be transitive.
Therefore, the relation $R$ is reflexive and transitive, but not symmetric.
So, the correct answer is Option D: $R$ is reflexive and transitive only.
#1075
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2006
AIEEE
KNOWLEDGE
4 Marks
Let $W$ denote the words in the English dictionary. Define the relation $R$ by $R = {(x, y) ∈ W × W |$ the words $x$ and $y$ have at least one letter in common}. Then, $R$ is
(A) reflexive, symmetric and not transitive
(B) reflexive, symmetric and transitive
(C) reflexive, not symmetric and transitive
(D) not reflexive, symmetric and transitive
Key: A
Sol:
Sol:
To determine the properties of the relation $R$, we analyze reflexivity, symmetry, and transitivity.
Reflexivity: A word always shares at least one letter with itself. So, $(x, x) ∈ R$ for all $x ∈ W$. Therefore, $R$ is reflexive.
Symmetry: If a word $x$ has a letter in common with word $y$, then $y$ also has a letter in common with $x$. So, if $(x, y) ∈ R$, then $(y, x) ∈ R$. Therefore, $R$ is symmetric.
Transitivity: Consider the words 'cat', 'bat', and 'bee'. 'cat' and 'bat' share the letter 'a', so (cat, bat) ∈ R. 'bat' and 'bee' share the letter 'b', so (bat, bee) ∈ R. However, 'cat' and 'bee' do not share any common letters, so (cat, bee) ∉ R. Therefore, $R$ is not transitive.
Thus, the relation $R$ is reflexive, symmetric, and not transitive.
#1074
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2008
AIEEE
KNOWLEDGE
4 Marks
Let $R$ be the real line. Consider the following subsets of the plane $R \times R$: $S = {(x, y) : y=x+1 ext{ and } 0<x<2}$ $T = {(x, y) : x - y ext{ is an integer }}$, Which one of the following is true ?
(A) Neither S nor T is an equivalence relation on R
(B) Both S and T are equivalence relation on R
(C) S is an equivalence relation on R but T is not
(D) T is an equivalence relation on R but S is not
Key: D
Sol:
Sol:
Given $S = {(x, y) : y = x + 1 ext{ and } 0 < x < 2}$. Since $x \ne x+1$ for any $x \in (0,2)$, we have $(x, x) \notin S$. Therefore, $S$ is not reflexive, and hence not an equivalence relation. Also $T = {(x, y) : x - y ext{ is an integer }}$. Since $x - x = 0$ is an integer for all $x \in R$, $T$ is reflexive. If $x - y$ is an integer, then $y - x$ is also an integer, so $T$ is symmetric. If $x - y$ is an integer and $y - z$ is an integer, then $(x - y) + (y - z) = x - z$ is also an integer. Therefore, $T$ is transitive. Hence $T$ is an equivalence relation.
#1073
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2009
AIEEE
KNOWLEDGE
4 Marks
If $A$, $B$ and $C$ are three sets such that $A \cap B = A \cap C$ and $A \cup B = A \cup C$, then :
(A) $A = C$
(B) $B = C$
(C) $A \cap B = \phi$
(D) $A = B$
Key: B
Sol:
Sol:
Given $A \cap B = A \cap C$ and $A \cup B = A \cup C$. From the principle of inclusion-exclusion: $|A \cup B| = |A| + |B| - |A \cap B|$ and $|A \cup C| = |A| + |C| - |A \cap C|$. Since $A \cup B = A \cup C$ and $A \cap B = A \cap C$, then $|A \cup B| = |A \cup C|$ and $|A \cap B| = |A \cap C|$. Thus, $|A| + |B| - |A \cap B| = |A| + |C| - |A \cap C|$. This simplifies to $|B| = |C|$. Since $A \cap B = A \cap C$ and $A \cup B = A \cup C$, it means that $B$ and $C$ contain the same elements and therefore are equal to each other ($B=C$).
#1072
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2010
AIEEE
KNOWLEDGE
4 Marks
Consider the following relations $R = \{(x, y) | x, y$ are real numbers and $x = wy$ for some rational number $w\}$; $S = \{(\frac{m}{n}, \frac{p}{q}) | m, n, p$ and $q$ are integers such that $n, q \neq 0$ and $qm = pn\}$. Then
(A) $R$ is an equivalence relation but $S$ is not an equivalence relation
(B) Neither $R$ nor $S$ is an equivalence relation
(C) $S$ is an equivalence relation but $R$ is not an equivalence relation
(D) $R$ and $S$ both are equivalence relations
Key: C
Sol:
Sol:
Relation $R$: $R = \{(x, y) | x, y$ are real numbers and $x = wy$ for some rational number $w\}$.
Reflexivity: For all $x$ in $R$, $x = 1 \cdot x$. Since $1$ is a rational number, every element is related to itself.
Symmetry: For all $x, y$ in $R$, if $x = wy$ for some rational $w$, then $y = \frac{1}{w}x$. However, if $w = 0$, then $\frac{1}{w}$ is undefined, and therefore, $R$ doesn't satisfy symmetry.
Transitivity: If $x = wy$ and $y = vz$ for some rational numbers $w$ and $v$, then $x = (wv)z$. Since the product of rational numbers is rational, if $x$ is related to $y$ and $y$ is related to $z$, then $x$ is related to $z$.
Therefore, $R$ is not an equivalence relation on $R$ since it does not satisfy the symmetry property.
Relation $S$: $S = \{(\frac{m}{n}, \frac{p}{q}) | m, n, p$ and $q$ are integers such that $n, q \neq 0$ and $qm = pn\}$.
Reflexivity: For all $\frac{m}{n}$, $\frac{m}{n} = \frac{m}{n}$. Since $n \neq 0$ and $m = m$, every element is related to itself.
Symmetry: For all $\frac{m}{n}, \frac{p}{q}$, if $qm = pn$, then $np = mq$. So if $\frac{m}{n}$ is related to $\frac{p}{q}$, then $\frac{p}{q}$ is related to $\frac{m}{n}$.
Transitivity: If $\frac{m}{n}R\frac{p}{q}$ and $\frac{p}{q}R\frac{r}{s}$ $\Rightarrow mq = np$ and $ps = rq$ $\Rightarrow mq \cdot ps = np \cdot rq$ $\Rightarrow ms = nr$ $\Rightarrow \frac{m}{n} = \frac{r}{s}$ $\Rightarrow \frac{m}{n}R\frac{r}{s}$.
So if $\frac{m}{n}$ is related to $\frac{p}{q}$ and $\frac{p}{q}$ is related to $\frac{r}{s}$, then $\frac{m}{n}$ is related to $\frac{r}{s}$. The relation $S$ is transitive.
Therefore, $S$ is an equivalence relation on the set of all fractions where the denominator is not zero.
In conclusion, $S$ is an equivalence relation but $R$ is not an equivalence relation.
#1071
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2011
AIEEE
KNOWLEDGE
4 Marks
Let $R$ be the set of real numbers. Statement I: $A = \{(x, y) \in R \times R: y - x \text{ is an integer }\}$ is an equivalence relation on $R$. Statement II: $B = \{(x,y) \in R \times R: x = \alpha y \text{ for some rational number } \alpha\}$ is an equivalence relation on $R$.
(A) Statement I is true, Statement II is true; Statement II is not a correct explanation for Statement I.
(B) Statement I is true, Statement II is false.
(C) Statement I is false, Statement II is true.
(D) Statement I is true, Statement II is true; Statement II is a correct explanation for Statement I.
Key: B
Sol:
Sol:
Statement I: $A = \{(x, y) \in R \times R: y - x \text{ is an integer }\}$. Reflexivity: For all $x \in R$, $x - x = 0$ which is an integer. Symmetry: For all $x, y \in R$, if $y - x$ is an integer, then $x - y = -(y - x)$ is also an integer. Transitivity: For all $x, y, z \in R$, if $y - x$ and $z - y$ are integers, then $(z - y) + (y - x) = z - x$ is also an integer. Therefore, $A$ is an equivalence relation on $R$. Statement II: $B = \{(x,y) \in R \times R: x = \alpha y \text{ for some rational number } \alpha\}$. Reflexivity: For all $x \in R$, $x = 1 \cdot x$. Since $1$ is a rational number, every element is related to itself. Symmetry: For all $x, y \in R$, if $x = \alpha y$ for some rational $\alpha$, then $y = \frac{1}{\alpha} x$. However, if $\alpha = 0$, then $\frac{1}{\alpha}$ is undefined, and therefore, $B$ doesn't satisfy symmetry. Transitivity: If $x = \alpha y$ and $y = \beta z$ for some rational numbers $\alpha$ and $\beta$, then $x = (\alpha \beta) z$. Since the product of rational numbers is rational, if $x$ is related to $y$ and $y$ is related to $z$, then $x$ is related to $z$. Therefore, $B$ is not an equivalence relation on $R$ since it does not satisfy the symmetry property. In conclusion, Statement I is true, and Statement II is false.
#1070
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2012
AIEEE 2012
KNOWLEDGE
4 Marks
Let $X = {1, 2, 3, 4, 5}$. The number of different ordered pairs $(Y, Z)$ that can be formed such that $Y \subseteq X$, $Z \subseteq X$ and $Y \cap Z$ is empty, is:
(A) $3^5$
(B) $2^5$
(C) $5^3$
(D) $5^2$
Key: A
Sol:
Sol:
For any element $x_i$ present in $X$, 4 cases arise while making subsets $Y$ and $Z$.
Case 1: $x_i \in Y, x_i \in Z \implies Y \cap Z \neq \emptyset$
Case 2: $x_i \in Y, x_i \notin Z \implies Y \cap Z = \emptyset$
Case 3: $x_i \notin Y, x_i \in Z \implies Y \cap Z = \emptyset$
Case 4: $x_i \notin Y, x_i \notin Z \implies Y \cap Z = \emptyset$
Therefore, for every element, the number of ways is $3$ for which $Y \cap Z = \emptyset$.
Thus, the total number of ways is $3 \times 3 \times 3 \times 3 \times 3 = 3^5$ since the number of elements in set $X$ is $5$.
#1069
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2015
JEE Main 2015 (Offline)
KNOWLEDGE
4 Marks
Let A and B be two sets containing four and two elements respectively. Then, the number of subsets of the set $A \times B$, each having atleast three elements are
(A) 219
(B) 256
(C) 275
(D) 510
Key: A
Sol:
Sol:
Given, $n(A) = 4$, $n(B) = 2$
$\Rightarrow n(A \times B) = 8$
Total number of subsets of set $(A \times B) = 2^8$
Number of subsets of set $A \times B$ having no element (i.e. $\phi$) = $1$
Number of subsets of set $A \times B$ having one element = $^8C_1$
Number of subsets of set $A \times B$ having two elements = $^8C_2$
$\therefore$ Number of subsets having atleast three elements = $2^8 - (1 + ^8C_1 + ^8C_2)$ = $2^8 - 1 - 8 - 28$ = $2^8 - 37$ = $256 - 37 = 219$
#1068
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2016
JEE Main 2016 (Online) 10th April Morning Slot
KNOWLEDGE
4 Marks
Let $P = {\theta : sin\theta - cos\theta = \sqrt{2}cos\theta}$ and $Q = {\theta : sin\theta + cos\theta = \sqrt{2}sin\theta}$ be two sets. Then
(A) $P \subset Q$ and $Q - P \neq \phi$
(B) $Q \nsubseteq P$
(C) $P \nsubseteq Q$
(D) $P = Q$
Key: D
Sol:
Sol:
Given, for set P:
$sin\theta - cos\theta = \sqrt{2}cos\theta$
$sin\theta = (\sqrt{2} + 1)cos\theta$
$cos\theta = (\sqrt{2} - 1)sin\theta$ ... (1)
Given, for set Q:
$sin\theta + cos\theta = \sqrt{2}sin\theta$
$cos\theta = (\sqrt{2} - 1)sin\theta$ ... (2)
From (1) and (2), P = Q
#1067
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2018
JEE Main 2018 (Online) 15th April Morning Slot
KNOWLEDGE
4 Marks
Consider the following two binary relations on the set $A = {a, b, c}$:
$R_1 = {(c, a), (b, b), (a, c), (c, c), (b, c), (a, a)}$ and
$R_2 = {(a, b), (b, a), (c, c), (c, a), (a, a), (b, b), (a, c)}$.
Then:
$R_1 = {(c, a), (b, b), (a, c), (c, c), (b, c), (a, a)}$ and
$R_2 = {(a, b), (b, a), (c, c), (c, a), (a, a), (b, b), (a, c)}$.
Then:
(A) both $R_1$ and $R_2$ are not symmetric.
(B) $R_1$ is not symmetric but it is transitive.
(C) $R_2$ is symmetric but it is not transitive.
(D) both $R_1$ and $R_2$ are transitive.
Key: C
Sol:
Sol:
Here, both $R_1$ and $R_2$ are symmetric, as for any $(x, y) \in R_1$, we have $(y, x) \in R_1$ and similarly for any $(x, y) \in R_2$, we have $(y, x) \in R_2$.
In $R_1$, $(b, c) \in R_1$, $(c, a) \in R_1$ but $(b, a) \notin R_1$.
Similarly, in $R_2$, $(b, a) \in R_2$, $(a, c) \in R_2$ but $(b, c) \notin R_2$.
Therefore, $R_1$ and $R_2$ are not transitive. Thus, $R_2$ is symmetric but not transitive.
#1066
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2018
JEE Main 2018 (Offline)
KNOWLEDGE
4 Marks
Two sets A and B are as under : A = {$(a, b) ∈ R × R : |a - 5| < 1$ and $|b - 5| < 1$}; B = {$(a, b) ∈ R × R : 4(a - 6)^2 + 9(b - 5)^2 ≤ 36$}; Then
(A) neither A ⊂ B nor B ⊂ A
(B) B ⊂ A
(C) A ⊂ B
(D) A ∩ B = 𝜙 ( an empty set )
Key: C
Sol:
Sol:
Given, $4(a-6)^2 + 9(b-5)^2 ≤ 36$. Let $a-6 = x$ and $b-5 = y$. Therefore, $4x^2 + 9y^2 ≤ 36$, which implies $\frac{x^2}{9} + \frac{y^2}{4} ≤ 1$. This is the equation of an ellipse.
According to set A, $|a-5| < 1$, which implies, since $a-6=x$, then $a-5 = x+1$. Thus $|x+1| < 1$, implying $-1 < x+1 < 1$, which leads to $-2 < x < 0$. Similarly, $|b-5| < 1$, implying $|y| < 1$, which leads to $-1 < y < 1$.
To check if the entire set A is inside of B, we can test a point of set A in the inequality $\frac{x^2}{9} + \frac{y^2}{4} ≤ 1$. Consider the point $(-2, 1)$. Substituting into the inequality gives LHS = $\frac{(-2)^2}{9} + \frac{1^2}{4} = \frac{4}{9} + \frac{1}{4} = \frac{25}{36} < 1$. Since the inequality holds, $(-2, 1)$ is inside the ellipse. Similarly, $(-2, -1)$ is also inside the ellipse. Hence, we can say that entire set A is inside of set B, therefore $A ⊂ B$.
#1065
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2018
JEE Main 2018 (Online) 16th April Morning Slot
KNOWLEDGE
4 Marks
Let $N$ denote the set of all natural numbers. Define two binary relations on $N$ as $R_1 = \{(x, y) \in N \times N : 2x + y = 10\}$ and $R_2 = \{(x, y) \in N \times N : x + 2y = 10\}$. Then :
(A) Range of $R_1$ is $\{2, 4, 8\}$.
(B) Range of $R_2$ is $\{1, 2, 3, 4\}$.
(C) Both $R_1$ and $R_2$ are symmetric relations.
(D) Both $R_1$ and $R_2$ are transitive relations.
Key: B
Sol:
Sol:
For $R_1$, $2x + y = 10$ and $x, y \in N$, the possible values for $x$ and $y$ are:
$x = 1, y = 8 \implies (1, 8)$
$x = 2, y = 6 \implies (2, 6)$
$x = 3, y = 4 \implies (3, 4)$
$x = 4, y = 2 \implies (4, 2)$
Therefore, $R_1 = \{(1, 8), (2, 6), (3, 4), (4, 2)\}$.
Hence, the range of $R_1$ is $\{2, 4, 6, 8\}$.
$R_1$ is not symmetric.
$R_1$ is not transitive as $(3, 4), (4, 2) \in R_1$, but $(3, 2) \notin R_1$.
For $R_2$, $x + 2y = 10$ and $x, y \in N$, the possible values for $x$ and $y$ are:
$x = 8, y = 1 \implies (8, 1)$
$x = 6, y = 2 \implies (6, 2)$
$x = 4, y = 3 \implies (4, 3)$
$x = 2, y = 4 \implies (2, 4)$
Therefore, $R_2 = \{(8, 1), (6, 2), (4, 3), (2, 4)\}$.
Hence, the range of $R_2 = \{1, 2, 3, 4\}$.
$R_2$ is not symmetric and transitive.
#1064
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2019
JEE Main 2019 (Online) 10th January Morning Slot
KNOWLEDGE
4 Marks
In a class of $140$ students numbered $1$ to $140$, all even numbered students opted Mathematics course, those whose number is divisible by $3$ opted Physics course and those whose number is divisible by $5$ opted Chemistry course. Then the number of students who did not opt for any of the three courses is
(A) $42$
(B) $102$
(C) $1$
(D) $38$
Key: D
Sol:
Sol:
Let $A$ be the set of students who opted for Mathematics, $B$ be the set of students who opted for Physics, and $C$ be the set of students who opted for Chemistry. We are given:
Total number of students $= 140$
$n(A) = \lfloor\frac{140}{2}\rfloor = 70$
$n(B) = \lfloor\frac{140}{3}\rfloor = 46$
$n(C) = \lfloor\frac{140}{5}\rfloor = 28$
$n(A \cap B) = \lfloor\frac{140}{6}\rfloor = 23$
$n(B \cap C) = \lfloor\frac{140}{15}\rfloor = 9$
$n(C \cap A) = \lfloor\frac{140}{10}\rfloor = 14$
$n(A \cap B \cap C) = \lfloor\frac{140}{30}\rfloor = 4$
Using the principle of inclusion-exclusion:
$n(A \cup B \cup C) = n(A) + n(B) + n(C) - n(A \cap B) - n(B \cap C) - n(C \cap A) + n(A \cap B \cap C)$
$n(A \cup B \cup C) = 70 + 46 + 28 - 23 - 9 - 14 + 4 = 102$
The number of students who did not opt for any of the three courses is:
$140 - n(A \cup B \cup C) = 140 - 102 = 38$
#1063
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2019
JEE Main 2019 (Online) 12th January Morning Slot
KNOWLEDGE
4 Marks
Let $S = {1, 2, 3, … , 100}$. The number of non-empty subsets A of S such that the product of elements in A is even is :
(A) $2^{50} – 1$
(B) $2^{50} (2^{50} – 1)$
(C) $2^{100} – 1$
(D) $2^{50} + 1$
Key: B
Sol:
Sol:
Let $S = {1, 2, 3, ..., 100}$. The total number of non-empty subsets is $2^{100} - 1$. The number of subsets with an odd product consists only of odd numbers. There are 50 odd numbers in the set $S$. So, the number of such subsets is $2^{50} - 1$. Therefore, the number of subsets with an even product is $(2^{100} - 1) - (2^{50} - 1) = 2^{100} - 2^{50} = 2^{50}(2^{50} - 1)$.
#1062
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2019
JEE Main 2019 (Online) 12th January Evening Slot
KNOWLEDGE
4 Marks
Let $Z$ be the set of integers. If $A = {x \in Z : 2(x + 2) (x^2 - 5x + 6) = 1}$ and $B = {x \in Z : -3 < 2x - 1 < 9}$, then the number of subsets of the set $A \times B$, is
(A) $2^{12}$
(B) $2^{18}$
(C) $2^{10}$
(D) $2^{15}$
Key: D
Sol:
Sol:
Given $A = {x \in Z : 2(x+2)(x^2 - 5x + 6) = 1}$.
Since $2(x+2)(x^2 - 5x + 6) = 1$, we can rewrite it as $2(x+2)(x^2 - 5x + 6) = 2^0$.
This implies that $x = -2, 2, 3$, so $A = {-2, 2, 3}$.
Also, $B = {x \in Z : -3 < 2x - 1 < 9}$.
Adding 1 to all sides, we get $-2 < 2x < 10$.
Dividing by 2, we get $-1 < x < 5$.
Thus, $B = {0, 1, 2, 3, 4}$.
Now, $A \times B$ has $3 \times 5 = 15$ elements.
The number of subsets of $A \times B$ is $2^{15}$.
#1061
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2019
JEE Main 2019 (Online) 9th April Evening Slot
KNOWLEDGE
4 Marks
Two newspapers A and B are published in a city. It is known that $25$% of the city populations reads A and $20$% reads B while $8$% reads both A and B. Further, $30$% of those who read A but not B look into advertisements and $40$% of those who read B but not A also look into advertisements, while $50$% of those who read both A and B look into advertisements. Then the percentage of the population who look into advertisement is :-
(A) $13.5$
(B) $13$
(C) $12.8$
(D) $13.9$
Key: D
Sol:
Sol:
Let the total population be $100$. Then:
People who read A only: $25 - 8 = 17$
People who read B only: $20 - 8 = 12$
People who read A and look into advertisements: $0.30 \times 17 = 5.1$
People who read B and look into advertisements: $0.40 \times 12 = 4.8$
People who read both A and B and look into advertisements: $0.50 \times 8 = 4$
Total percentage of people who look into advertisements: $5.1 + 4.8 + 4 = 13.9$
Therefore, the percentage of the population who look into advertisement is $13.9$%.
#1060
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
2019
JEE Main 2019 (Online) 12th April Evening Slot
KNOWLEDGE
4 Marks
Let A, B and C be sets such that $\phi \neq A \cap B \subseteq C$. Then which of the following statements is not true ?
(A) If (A – B) $\subseteq$ C, then A $\subseteq$ C
(B) B $\cap$ C $\neq$ $\phi$
(C) (C $\cup$ A) $\cap$ (C $\cup$ B) = C
(D) If (A – C) $\subseteq$ B, then A $\subseteq$ B
Key: D
Sol:
Sol:
The question provides that $A \cap B \subseteq C$ and $A \cap B \neq \phi$. Analyzing each statement:
Statement A: If $(A - B) \subseteq C$, then $A \subseteq C$. This statement can be verified using Venn diagrams. If the part of A that is not in B is contained in C, then A is a subset of C.
Statement B: $B \cap C \neq \phi$. This means that the intersection of B and C is not empty. Given that $A\cap B \subseteq C$, this is true.
Statement C: $(C \cup A) \cap (C \cup B) = C$. Using the distributive property of sets, $(C \cup A) \cap (C \cup B) = C \cup (A \cap B)$. Since $A \cap B \subseteq C$, then $C \cup (A \cap B) = C$. So, this statement is true.
Statement D: If $(A - C) \subseteq B$, then $A \subseteq B$. This statement is NOT necessarily true. It is possible to have $A - C \subseteq B$, $A \cap B \subseteq C$ and $A \cap B \neq \phi$, but it does NOT require that $A \subseteq B$. This is because A can contain elements outside of B that are also outside of C.
Therefore, the statement that is not true is D.