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#994
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
HARD
2025
JEE Main 2025 (Online) 8th April Evening Shift
Competency
4 Marks
Let A = {0, 1, 2, 3, 4, 5}. Let R be a relation on A defined by (x, y) ∈ R if and only if max{x, y} ∈ {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 evaluate the relation $R$ on the set $A = {0, 1, 2, 3, 4, 5}$, we first need to understand the conditions for an element $(x, y)$ to be in $R$. Specifically, $(x, y) ∈ R$ if and only if $max{x,y} ∈ {3,4}$.
Considering this, let's list the pairs:
For $max{x, y} = 3$, the possible pairs are:
$(0, 3), (3, 0), (1, 3), (3, 1), (2, 3), (3, 2), (3, 3)$
For $max{x, y} = 4$, the possible pairs are:
$(0, 4), (4, 0), (1, 4), (4, 1), (2, 4), (4, 2), (3, 4), (4, 3), (4, 4)$
Combining these, the set $R$ consists of the following elements:
$R = {(0, 3), (3, 0), (1, 3), (3, 1), (2, 3), (3, 2), (3, 3), (0, 4), (4, 0), (1, 4), (4, 1), (2, 4), (4, 2), (3, 4), (4, 3), (4, 4)}$
This gives us a total of 16 elements in $R$, not 18 as initially claimed in statement $S1$.
Next, we analyze the properties of the relation $R$:
Reflexivity: A relation is reflexive if $(x, x) ∈ R$ for all $x ∈ A$. For example, $(0, 0), (1, 1), (2, 2)$ are not in $R$, so $R$ is not reflexive.
Symmetry: A relation is symmetric if whenever $(a, b) ∈ R$, then $(b, a) ∈ R$ as well. For all pairs $(x, y)$ listed, both $(x, y)$ and $(y, x)$ are present. Thus, $R$ is symmetric.
Transitivity: A relation is transitive if whenever $(a, b) ∈ R$ and $(b, c) ∈ R$, then $(a, c) ∈ R$. An example where transitivity fails is $(0, 3)$ and $(3, 1)$ are in $R$ but $(0, 1)$ is not in $R$. Therefore, $R$ is not transitive.
In conclusion, statement $S2$ is correct as $R$ is symmetric but neither reflexive nor transitive.
#993
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 28th January Morning Shift
KNOWLEDGE
4 Marks
Three defective oranges are accidently mixed with seven good ones and on looking at them, it is not possible to differentiate between them. Two oranges are drawn at random from the lot. If $x$ denote the number of defective oranges, then the variance of $x$ is
(A) 26/75
(B) 14/25
(C) 18/25
(D) 28/75
Key: D
Sol:
Sol:
Probability distribution
$x = 0$, $p = \frac{^7C_2}{^{10}C_2} = \frac{42}{90}$
$x = 1$, $p = \frac{^7C_1 \times ^3C_1}{^{10}C_2} = \frac{42}{90}$
$x = 2$, $p = \frac{^3C_2}{^{10}C_2} = \frac{6}{90}$
Now,
$\mu = \sum x_i p_i = \frac{42}{90} + \frac{12}{90} = \frac{54}{90}$
$\sigma^2 = \sum p_i x_i^2 - \mu^2 = \frac{42}{90} + \frac{24}{90} - (\frac{54}{90})^2$
$\Rightarrow \frac{66}{90} - (\frac{54}{90})^2$
$\sigma^2 \Rightarrow \frac{28}{75}$
#992
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 28th January Morning Shift
KNOWLEDGE
4 Marks
Two number $k_1$ and $k_2$ are randomly chosen from the set of natural numbers. Then, the probability that the value of $i^{k_1} + i^{k_2}$, ($i = \sqrt{-1}$) is non-zero, equals
(A) $\frac{3}{4}$
(B) $\frac{1}{2}$
(C) $\frac{1}{4}$
(D) $\frac{2}{3}$
Key: A
Sol:
Sol:
$i^{k_1} + i^{k_2} \ne 0 \Rightarrow i^{k_1} \rightarrow 4$ option for $i, -1, -i, 1$
Total cases $ \Rightarrow 4 \times 4 = 16$
Unfovourble cases $ \Rightarrow i^{k_1} + i^{k_2} = 0$
$ \{\begin{array}{c}1, -1 \\ -1, 1 \\ i, -i \\ -i, i\end{array}\}$
4 Cases $\Rightarrow$ Probability $ = \frac{16-4}{16} = \frac{3}{4}$
#991
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 28th January Evening Shift
KNOWLEDGE
4 Marks
Let S be the set of all the words that can be formed by arranging all the letters of the word GARDEN. From the set S, one word is selected at random. The probability that the selected word will NOT have vowels in alphabetical order is:
(A) $\frac{1}{4}$
(B) $\frac{1}{2}$
(C) $\frac{1}{3}$
(D) $\frac{2}{3}$
Key: B
Sol:
Sol:
A, E,G R D N
Probabllity $(P) = \frac{\text{favourable case}}{\text{Total case}}$
(when A & E are in order)
Total case = $6!$
Favourable case = ${6}C_2 . 4! = (15)4! = (30)4!$
$P = \frac{(15)4!}{(30)4!} = \frac{1}{2}$
Probability when not in order = $1 - \frac{1}{2} = \frac{1}{2}$
#990
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 28th January Evening Shift
KNOWLEDGE
4 Marks
Bag $B_1$ contains 6 white and 4 blue balls, Bag $B_2$ contains 4 white and 6 blue balls, and Bag $B_3$ contains 5 white and 5 blue balls. One of the bags is selected at random and a ball is drawn from it. If the ball is white, then the probability that the ball is drawn from Bag $B_2$ is:
(A) $\frac{2}{5}$
(B) $\frac{4}{15}$
(C) $\frac{1}{3}$
(D) $\frac{2}{3}$
Key: B
Sol:
Sol:
$E_1$: Bag $B_1$ is selected
$B_1$: 6 W 4 B
$B_2$: 4 W 6 B
$B_3$: 5 W 5 B
$E_2$: bag $B_2$ is selected
We have to find $P(\frac{E_2}{A})$
$P(\frac{E_2}{A}) = \frac{P(E_2)P(\frac{A}{E_2})}{P(E_1)P(\frac{A}{E_1}) + P(E_2)P(\frac{A}{E_2}) + P(E_3)P(\frac{A}{E_3})} = \frac{\frac{1}{3} \times \frac{4}{10}}{\frac{1}{3} \times \frac{6}{10} + \frac{1}{3} \times \frac{4}{10} + \frac{1}{3} \times \frac{5}{10}} = \frac{4}{15}$
#989
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 29th January Evening Shift
KNOWLEDGE
4 Marks
Bag 1 contains 4 white balls and 5 black balls, and Bag 2 contains n white balls and 3 black balls. One ball is drawn randomly from Bag 1 and transferred to Bag 2. A ball is then drawn randomly from Bag 2. If the probability, that the ball drawn is white, is $\frac{29}{45}$, then n is equal to:
(A) 5
(B) 6
(C) 4
(D) 3
Key: B
Sol:
Sol:
Bag $1 = \{4 W, 5 B\}$
Bag $2 = \{nW, 3B\}$
$P(\frac{W}{Bag2}) = \frac{29}{45}$
$\Rightarrow P(\frac{W}{B_1}) \times P(\frac{W}{B_2}) + P(\frac{B}{B_1}) \times P(\frac{W}{B_2}) = \frac{29}{45}$
$\frac{4}{9} \times \frac{n+1}{n+4} + \frac{5}{9} \times \frac{n}{n+4} = \frac{29}{45}$
$n = 6$
#988
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
EASY
2025
JEE Main 2025 (Online) 2nd April Evening Shift
KNOWLEDGE
4 Marks
Given three indentical bags each containing $10$ balls, whose colours are as follows:
| | Red | Blue | Green |
|--------|-----|------|-------|
| Bag I | $3$ | $2$ | $5$ |
| Bag II | $4$ | $3$ | $3$ |
| Bag III| $5$ | $1$ | $4$ |
A person chooses a bag at random and takes out a ball. If the ball is Red, the probability that it is from bag I is $p$ and if the ball is Green, the probability that it is from bag III is $q$, then the value of $(\frac{1}{p} + \frac{1}{q})$ is:
| | Red | Blue | Green |
|--------|-----|------|-------|
| Bag I | $3$ | $2$ | $5$ |
| Bag II | $4$ | $3$ | $3$ |
| Bag III| $5$ | $1$ | $4$ |
A person chooses a bag at random and takes out a ball. If the ball is Red, the probability that it is from bag I is $p$ and if the ball is Green, the probability that it is from bag III is $q$, then the value of $(\frac{1}{p} + \frac{1}{q})$ is:
(A) $6$
(B) $9$
(C) $7$
(D) $8$
Key: C
Sol:
Sol:
Probability that a Red ball comes from Bag I ($p$):
$p(B_1/R) = \frac{p(B_1) \cdot p(R/B_1)}{p(R)}$
Substituting the values,
$p(B_1/R) = \frac{\frac{1}{3} \times \frac{3}{10}}{\frac{1}{3} \times \frac{3}{10} + \frac{1}{3} \times \frac{4}{10} + \frac{1}{3} \times \frac{5}{10}}$
Simplify to find $p$:
$=\frac{\frac{1}{10}}{\frac{1}{3}(1.2)} = \frac{1}{4}$
So, $p = \frac{1}{4}$.
Probability that a Green ball comes from Bag III ($q$):
$p(B_3/G) = \frac{p(B_3) \cdot p(G/B_3)}{p(G)}$
Substitute the values,
$p(B_3/G) = \frac{\frac{1}{3} \times \frac{4}{10}}{\frac{1}{3} \times \frac{5}{10} + \frac{1}{3} \times \frac{3}{10} + \frac{1}{3} \times \frac{4}{10}}$
Simplify to find $q$:
$=\frac{\frac{2}{15}}{\frac{1}{3} \times 1.2} = \frac{1}{3}$
So, $q = \frac{1}{3}$.
Calculation of $(\frac{1}{p} + \frac{1}{q})$:
$\frac{1}{p} = 4$, $\frac{1}{q} = 3$
Therefore,
$(\frac{1}{p} + \frac{1}{q}) = 4 + 3 = 7$
#987
Mathematics
Sets, Relations, and Functions
MCQ_SINGLE
APPLY
HARD
2025
JEE Main 2025 (Online) 3rd April Evening Shift
Competency
4 Marks
If the probability that the random variable $X$ takes the value $x$ is given by
$P(X=x) = k(x+1)3^{-x}, x = 0, 1, 2, 3 \dots$, where $k$ is a constant, then $P(X \geq 3)$ is equal to
$P(X=x) = k(x+1)3^{-x}, x = 0, 1, 2, 3 \dots$, where $k$ is a constant, then $P(X \geq 3)$ is equal to
(A) $\frac{1}{9}$
(B) $\frac{8}{27}$
(C) $\frac{7}{27}$
(D) $\frac{4}{9}$
Key: A
Sol:
Sol:
To find $P(X \geq 3)$, we first determine the constant $k$ using the total probability for $X$.
The probability $P(X = x)$ is given by:
$P(X= x) = k(x+1) \cdot 3^{-x}, x= 0,1,2,3,\dots$
The total probability must equal 1:
$s = \sum_{x=0}^{\infty} k(x+1) \cdot 3^{-x}$
Calculating that series:
$s = k3^0 + 2\frac{k}{3} + 3\frac{k}{3^2} + \dots$
Therefore, dividing the series by 3:
$\frac{s}{3} = \frac{k}{3} + 2\frac{k}{3^2} + \dots$
Subtracting these:
$s - \frac{s}{3} = k + \frac{k}{3} + \frac{k}{3^2} + \dots$
The resulting series is a geometric series:
$2\frac{s}{3} = k(1 + \frac{1}{3} + \frac{1}{3^2} + \dots )$
The sum of the infinite geometric series is:
$2\frac{s}{3} = k \cdot \frac{1}{1 - \frac{1}{3}} = \frac{3k}{2}$
Equating:
$s = \frac{9k}{4} = 1$
Thus, solving for $k$:
$k = \frac{4}{9}$
Next, compute $P(X \geq 3)$:
$P(X \geq 3) = 1 - (P(X=0) + P(X=1) + P(X=2))$
Calculating these:
$P(X=0) = k = \frac{4}{9}$
$P(X=1) = 2\frac{k}{3} = \frac{8}{27}$
$P(X=2) = 3\frac{k}{9} = \frac{4}{27}$
Adding these probabilities:
$P(X=0) + P(X=1) + P(X=2) = \frac{4}{9} + \frac{8}{27} + \frac{4}{27} = \frac{8}{9}$
Finally, calculate $P(X \geq 3)$:
$P(X \geq 3) = 1 - \frac{8}{9} = \frac{1}{9}$
#986
Mathematics
Statistics and Probability
MCQ_SINGLE
APPLY
HARD
2025
JEE Main 2025 (Online) 4th April Morning Shift
Competency
4 Marks
A box contains 10 pens of which 3 are defective. A sample of 2 pens is drawn at random and let $X$ denote the number of defective pens. Then the variance of $X$ is
(A) $\frac{11}{15}$
(B) $\frac{2}{15}$
(C) $\frac{3}{5}$
(D) $\frac{28}{75}$
Key: D
Sol:
Sol:
$X$\n$P(X)S$\n$XP(X)$\n$\left(X_i-\mu\right)^2$ SP_i X\left(X_i-\mu\right)^2$\n$X=0$\n$\frac{{}^7 C_2}{{}^{10} C_2}$\n0\nS\left(0-\frac{3}{5}\right)^2$\n$\frac{7}{15}\left(\frac{9}
#964
Mathematics
Practice
MCQ_SINGLE
APPLY
HARD
AI Import
Competency
1 Marks
Let A be the set of all functions $f: \mathbb{Z} \rightarrow \mathbb{Z}$ and R be a relation on A such that $R = \{(f, g): f(0) = g(1)$ and $f(1) = g(0)\}$. Then R is :
(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:
Symmetric but neither reflective nor transitive
#963
Mathematics
Practice
MCQ_SINGLE
APPLY
HARD
AI Import
Competency
1 Marks
Let A = {1, 2, 3, ...., 100} and R be a relation on A such that R = {(a, b): a = 2b+1}. Let (a1, аг), (аг, аз), (аз, а4),...., (ak, ak+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 :
equal to :
(A) 6
(B) 8
(C) 7
(D) 5
Key: D
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.
#962
Mathematics
Practice
MCQ_SINGLE
APPLY
HARD
Smart Import
Competency
1 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 < 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
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:
18
#961
Mathematics
Practice
MCQ_SINGLE
APPLY
MEDIUM
Competency
Marks
Let A = {-2, -1, 0, 1, 2, 3}. Let R be a relation on A defined by Ry if and only if y = max{x, 1}. Let I 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
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:
#960
Mathematics
Practice
MCQ_SINGLE
APPLY
HARD
2025
JEE Main 2025
Competency
0 Marks
Let A = {0, 1, 2, 3, 4, 5}. Let R be a relation on A defined by (x, y) ∈ R if and only if max{x,y} ∈ {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:
ok
#716
Mathematics
Practice
MCQ_SINGLE
APPLY
MEDIUM
2023
KNOWLEDGE
4 Marks
The number of real solutions of the equation x^2 + 5|x| + 6 = 0 is:
Key: 0
Sol:
Sol:
Since |x| is always non-negative, x^2 + 5|x| + 6 is the sum of positive terms plus 6, which can never be zero. Thus, no real solution.
#715
Mathematics
Practice
ASSERTION_REASON
APPLY
MEDIUM
2020
Competency
4 Marks
Assertion: The boiling point of water is higher at lower elevations. Reason: Atmospheric pressure increases as elevation decreases.
Key: Both true and R explains A
Sol:
Sol:
Boiling occurs when vapor pressure equals atmospheric pressure. Higher pressure requires higher temperature.
#714
Mathematics
Practice
MCQ_SINGLE
APPLY
MEDIUM
2021
KNOWLEDGE
4 Marks
A block of mass m is placed on a smooth wedge of inclination θ. The whole system is accelerated horizontally so that the block does not slip. The acceleration is:
Key: g tan θ
Sol:
Sol:
For the block to remain stationary relative to the wedge, the pseudo force ma must balance the component of gravity along the incline. ma cosθ = mg sinθ => a = g tanθ.
#713
Mathematics
Practice
MCQ_MULTI
REMEMBER
EASY
2022
KNOWLEDGE
4 Marks
Which of the following ores contain Iron?
Key: Haematite, Magnetite
Sol:
Sol:
Haematite is Fe2O3 and Magnetite is Fe3O4. Bauxite is Al, Malachite is Cu.
#712
Mathematics
Practice
MCQ_SINGLE
APPLY
MEDIUM
2023
KNOWLEDGE
4 Marks
If the complex number z satisfies |z| = 1 and z ≠ -1, then z/(1+z^2) is purely:
Key: Real
Sol:
Sol:
Let z = e^(iθ). Then z/(1+z^2) = e^(iθ) / (1 + e^(2iθ)). Simplifying this using Euler formula results in a real number.
#708
Mathematics
Practice
MCQ_MULTI
REMEMBER
EASY
2022
KNOWLEDGE
4 Marks
Which of the following compounds show Hydrogen bonding?
Key: A, C
Sol:
Sol:
Hydrogen bonding occurs when H is bonded to highly electronegative atoms like F, O, or N.