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CBSE - Class 12 Mathematics Matrices Worksheet
EXERCISE 3.1
Worksheet Answers
Solution:
Two matrices $A = [a_{ij}]$ and $B = [b_{ij}]$ are said to be equal if and only if:
[Definition of Equality of Matrices]
The given matrices are:
$A = \begin{bmatrix} 4 & 3 \\ x & 5 \end{bmatrix}$ (Order: $2 \times 2$)
$B = \begin{bmatrix} y & z \\ 1 & 5 \end{bmatrix}$ (Order: $2 \times 2$)
Since both matrices have an order of $2 \times 2$, the equality is well-defined. [Per the condition of equality for matrices of same dimensions].
By equating the elements at each position $(i, j)$ from matrix $A$ to matrix $B$:
| Position $(i, j)$ | Equation |
|---|---|
| Row 1, Column 1 | $4 = y$ |
| Row 1, Column 2 | $3 = z$ |
| Row 2, Column 1 | $x = 1$ |
| Row 2, Column 2 | $5 = 5$ (Identity holds) |
From the equations derived in Step 3, we directly extract the values:
Final Solution: x = 1, y = 4, z = 3
Solution:
A $3 \times 4$ matrix $A$ consists of $3$ rows and $4$ columns. The general form of the matrix is represented as:
$A = \begin{bmatrix} a_{11} & a_{12} & a_{13} & a_{14} \\ a_{21} & a_{22} & a_{23} & a_{24} \\ a_{31} & a_{32} & a_{33} & a_{34} \end{bmatrix}$
Each element $a_{ij}$ is defined by the rule $a_{ij} = 2i - j$, where $i$ denotes the row index ($i \in \{1, 2, 3\}$) and $j$ denotes the column index ($j \in \{1, 2, 3, 4\}$).
We evaluate each element systematically by substituting the indices into the given formula $a_{ij} = 2i - j$:
| Row ($i$) | $j=1$ | $j=2$ | $j=3$ | $j=4$ |
|---|---|---|---|---|
| $i=1$ | $2(1)-1 = 1$ | $2(1)-2 = 0$ | $2(1)-3 = -1$ | $2(1)-4 = -2$ |
| $i=2$ | $2(2)-1 = 3$ | $2(2)-2 = 2$ | $2(2)-3 = 1$ | $2(2)-4 = 0$ |
| $i=3$ | $2(3)-1 = 5$ | $2(3)-2 = 4$ | $2(3)-3 = 3$ | $2(3)-4 = 2$ |
Substituting the calculated values into the general matrix structure:
$A = \begin{bmatrix} 1 & 0 & -1 & -2 \\ 3 & 2 & 1 & 0 \\ 5 & 4 & 3 & 2 \end{bmatrix}$
Final Solution: The constructed matrix is $A = \begin{bmatrix} 1 & 0 & -1 & -2 \\ 3 & 2 & 1 & 0 \\ 5 & 4 & 3 & 2 \end{bmatrix}$
Solution:
The given matrix $A$ is presented as an array of elements organized into horizontal rows and vertical columns:
$A = \begin{bmatrix} 2 & 5 & 19 & -7 \\ 35 & -2 & \frac{5}{2} & 12 \\ \sqrt{3} & 1 & -5 & 17 \end{bmatrix}$By inspection, we define the dimensions of the matrix as follows:
[Per the definition of Matrix Algebra], the order of a matrix is denoted as $m \times n$, where $m$ represents the number of rows and $n$ represents the number of columns. This notation identifies the dimensions of the rectangular array.
Substituting the identified values into the $m \times n$ format:
$m = 3$Final Solution: The order of the matrix $A$ is $3 \times 4$.
Solution:
The given problem specifies a matrix of order $m \times n$, where $m = 3$ and $n = 3$. The total number of entries (elements) in the matrix is determined by the product of the number of rows and the number of columns [Definition of Matrix Order].
Total number of entries ($N$) = $m \times n = 3 \times 3 = 9$.
For each individual position $(i, j)$ in the $3 \times 3$ matrix, the allowed values are restricted to the set $\{0, 1\}$.
Since each of the $N$ positions in the matrix is independent and can be filled by any of the $k$ choices, the total number of possible matrices is given by the Fundamental Counting Principle [Permutation and Combination Axiom].
Total matrices = $k \times k \times \dots \times k$ ($N$ times)
Total matrices = $k^N$
Substitute the identified values into the derived formula:
$k = 2$
$N = 9$
Total matrices = $2^9$
| Calculation Step | Result |
|---|---|
| $2^1$ | 2 |
| $2^2$ | 4 |
| $2^3$ | 8 |
| $2^4$ | 16 |
| $2^5$ | 32 |
| $2^6$ | 64 |
| $2^7$ | 128 |
| $2^8$ | 256 |
| $2^9$ | 512 |
Final Solution: The number of all possible $3 \times 3$ matrices with entries 0 or 1 is $512$.
Solution:
Two matrices $A = [a_{ij}]$ and $B = [b_{ij}]$ are said to be equal if and only if they are of the same order and their corresponding elements are equal [Definition of Equality of Matrices]. Both given matrices are of order $2 \times 2$. Thus, we equate corresponding elements:
$\begin{bmatrix} 3x+7 & 5 \\ y+1 & 2-3x \end{bmatrix} = \begin{bmatrix} 0 & y-2 \\ 8 & 4 \end{bmatrix}$
Equating the elements at specific positions $(i, j)$:
Solving for $x$:
From (Equation 1):
$3x = -7 \implies x = -\frac{7}{3}$From (Equation 4):
$-3x = 4 - 2 \implies -3x = 2 \implies x = -\frac{2}{3}$Solving for $y$:
From (Equation 2):
$y = 5 + 2 \implies y = 7$From (Equation 3):
$y = 8 - 1 \implies y = 7$For the matrices to be equal, the value of $x$ must satisfy both (Equation 1) and (Equation 4) simultaneously. As derived, (Equation 1) yields $x = -\frac{7}{3}$ while (Equation 4) yields $x = -\frac{2}{3}$. Since these values are inconsistent ($-\frac{7}{3} \neq -\frac{2}{3}$), there exists no single value of $x$ that satisfies the equality for both elements $a_{11}$ and $a_{22}$ concurrently.
| Element Position | Constraint Value |
|---|---|
| $a_{11}$ vs $b_{11}$ | $x = -7/3$ |
| $a_{22}$ vs $b_{22}$ | $x = -2/3$ |
Since the requirements for $x$ are contradictory, the matrix equality cannot be satisfied for any pair $(x, y)$.
Final Solution: The values of $x$ and $y$ for which the matrices are equal cannot be determined; therefore, the correct option is "Not possible to find".
Solution:
A matrix $A$ of order $m \times n$ is a rectangular array of numbers arranged in $m$ rows and $n$ columns. For a $2 \times 2$ matrix, the general form is defined as:
$A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}$where $i$ denotes the row index and $j$ denotes the column index, with $i, j \in \{1, 2\}$. [Definition of a Matrix, NCERT Mathematics Textbook for Class XII].
Given the governing formula $a_{ij} = \frac{(i+j)^2}{2}$, we calculate each element systematically:
Substituting the computed values back into the general $2 \times 2$ matrix structure:
$A = \begin{bmatrix} 2 & 4.5 \\ 4.5 & 8 \end{bmatrix}$Final Solution: The matrix $A$ is given by $\begin{bmatrix} 2 & 4.5 \\ 4.5 & 8 \end{bmatrix}$.
Solution:
An $m \times n$ matrix is defined by its dimensions, where $m$ represents the number of rows and $n$ represents the number of columns. The total number of elements $N$ in such a matrix is given by the product of the number of rows and the number of columns: $N = m \times n$ [By the Definition of Matrix Order, where $m, n \in \mathbb{N}$]. To find all possible orders for a matrix with $N$ elements, we must identify all possible ordered pairs $(m, n)$ such that their product equals $N$.
Given $N = 18$, we seek all pairs of natural numbers $(m, n)$ such that $m \times n = 18$. We identify these by listing the factors of 18:
| Number of Rows ($m$) | Number of Columns ($n$) | Order ($m \times n$) |
|---|---|---|
| 1 | 18 | $1 \times 18$ |
| 2 | 9 | $2 \times 9$ |
| 3 | 6 | $3 \times 6$ |
| 6 | 3 | $6 \times 3$ |
| 9 | 2 | $9 \times 2$ |
| 18 | 1 | $18 \times 1$ |
Given $N = 5$, we identify the factors of 5. Since 5 is a prime number [By the Fundamental Theorem of Arithmetic], its only divisors are 1 and 5.
The possible orders are determined by the set of all divisor pairs of the given integer $N$.
Final Solution: For 18 elements, the possible orders are $1 \times 18$, $2 \times 9$, $3 \times 6$, $6 \times 3$, $9 \times 2$, and $18 \times 1$. For 5 elements, the possible orders are $1 \times 5$ and $5 \times 1$.
Solution:
By the definition of equality of matrices, two matrices are equal if and only if their corresponding elements are identical [Equality of Matrices Definition]. Given the column matrices of order $3 \times 1$, we equate the individual elements to form a system of three linear equations:
Substitute Eq (2) into Eq (1) to isolate the variable $y$:
$(x + z) + y = 9$
$5 + y = 9$ [Substituting $x + z = 5$ from Eq (2)]
$y = 9 - 5$
$y = 4$
Substitute the value of $y = 4$ into Eq (3) to find $z$:
$4 + z = 7$ [Substituting $y = 4$ into Eq (3)]
$z = 7 - 4$
$z = 3$
Substitute the value of $z = 3$ into Eq (2) to find $x$:
$x + 3 = 5$ [Substituting $z = 3$ into Eq (2)]
$x = 5 - 3$
$x = 2$
We verify the values by substituting $x=2, y=4, z=3$ into Eq (1):
$2 + 4 + 3 = 9$
$9 = 9$ [LHS = RHS; Solution is consistent]
Final Solution: $x = 2, y = 4, z = 3$
Solution:
Two matrices are considered equal if and only if they have the same order and their corresponding elements are identical [Definition of Matrix Equality]. Given the equation:
$\begin{bmatrix} x+y & 2 \\ 5+z & xy \end{bmatrix} = \begin{bmatrix} 6 & 2 \\ 5 & 8 \end{bmatrix}$
By equating the corresponding elements, we derive the following system of non-linear equations:
From (Eq. 2), we isolate $z$:
$5 + z = 5$
$z = 5 - 5$
$z = 0$ [Additive Inverse Property]
We use (Eq. 1) to express $y$ in terms of $x$:
$y = 6 - x$ (Eq. 4)
Substitute (Eq. 4) into (Eq. 3):
$x(6 - x) = 8$
$6x - x^2 = 8$
$x^2 - 6x + 8 = 0$ [Rearranging into standard Quadratic Form $ax^2 + bx + c = 0$]
Applying the factorization method: find two numbers that multiply to $8$ and add to $-6$. These numbers are $-2$ and $-4$.
$(x - 2)(x - 4) = 0$
This yields two potential values for $x$:
$x = 2$ or $x = 4$
Using (Eq. 4) $y = 6 - x$:
| Case | $x$ value | $y = 6 - x$ |
|---|---|---|
| Case 1 | $x = 2$ | $y = 6 - 2 = 4$ |
| Case 2 | $x = 4$ | $y = 6 - 4 = 2$ |
The values are $x = 2, y = 4, z = 0$ OR $x = 4, y = 2, z = 0$.
Solution:
Given the matrix $A$:
$A = \begin{bmatrix} 2 & 5 & 19 & -7 \\ 35 & -2 & \frac{5}{2} & 12 \\ \sqrt{3} & 1 & -5 & 17 \end{bmatrix}$
To determine the number of elements, we first identify the dimensions (order) of the matrix. The order of a matrix is defined as $m \times n$, where $m$ is the number of rows and $n$ is the number of columns [Definition of Matrix Order].
Therefore, the order of matrix $A$ is $3 \times 4$.
The total number of elements in a matrix $A$ of order $m \times n$ is given by the product of the number of rows and the number of columns [Fundamental Counting Principle].
$\text{Total elements} = m \times n$
Substituting the values derived in Step 1:
$\text{Total elements} = 3 \times 4 = 12$
Final Solution: The number of elements in the given matrix is 12.
Solution:
An element of a matrix is denoted by $a_{ij}$, where $i$ represents the row index and $j$ represents the column index. The index $i$ corresponds to the horizontal arrangement, and $j$ corresponds to the vertical arrangement of the element within the grid [Per the Definition of Matrix Notation].
The matrix $A$ is provided as:
$A = \begin{bmatrix} a_{11} & a_{12} & a_{13} & a_{14} \\ a_{21} & a_{22} & a_{23} & a_{24} \\ a_{31} & a_{32} & a_{33} & a_{34} \end{bmatrix} = \begin{bmatrix} 2 & 5 & 19 & -7 \\ 35 & -2 & \frac{5}{2} & 12 \\ \sqrt{3} & 1 & -5 & 17 \end{bmatrix}$By mapping the indices $(i, j)$ to the corresponding numerical values in the matrix, we extract the required components:
| Element Notation | Row Index ($i$) | Column Index ($j$) | Extracted Value |
|---|---|---|---|
| $a_{13}$ | 1 | 3 | $19$ |
| $a_{21}$ | 2 | 1 | $35$ |
| $a_{33}$ | 3 | 3 | $-5$ |
| $a_{24}$ | 2 | 4 | $12$ |
| $a_{23}$ | 2 | 3 | $\frac{5}{2}$ |
Final Solution: $a_{13} = 19, a_{21} = 35, a_{33} = -5, a_{24} = 12, a_{23} = \frac{5}{2}$
Solution:
An $m \times n$ matrix is defined by $m$ rows and $n$ columns. The total number of elements in such a matrix is given by the product of the number of rows and the number of columns, denoted as $N = m \times n$ [Per the definition of the order of a matrix]. To find all possible orders for a matrix with $N$ elements, we must identify all unique factor pairs $(m, n)$ of the integer $N$, where $m, n \in \mathbb{N}$.
To find the possible orders for $N = 24$, we determine all positive integer factor pairs of 24. We systematically test divisors of 24:
| Possible Orders ($m \times n$) |
|---|
| $1 \times 24, 24 \times 1, 2 \times 12, 12 \times 2, 3 \times 8, 8 \times 3, 4 \times 6, 6 \times 4$ |
Since 13 is a prime number, its only divisors are 1 and itself [Per the Fundamental Theorem of Arithmetic]. Therefore, the only possible factor pairs are:
Final Solution: For 24 elements, the possible orders are: $1 \times 24, 24 \times 1, 2 \times 12, 12 \times 2, 3 \times 8, 8 \times 3, 4 \times 6, 6 \times 4$. For 13 elements, the possible orders are: $1 \times 13$ and $13 \times 1$.
Solution:
For a $2 \times 2$ matrix $A$, the general representation is defined as:
$A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}$Where $i$ represents the row index and $j$ represents the column index [Per the definition of Matrix Dimensions $m \times n$].
Given the formula $a_{ij} = \frac{i}{j}$, we calculate each element systematically:
Substituting the calculated values into the general $2 \times 2$ matrix structure:
$A = \begin{bmatrix} 1 & \frac{1}{2} \\ 2 & 1 \end{bmatrix}$Final Solution: $A = \begin{bmatrix} 1 & \frac{1}{2} \\ 2 & 1 \end{bmatrix}$
Solution:
A matrix $A$ of order $2 \times 2$ is defined by its rows ($i$) and columns ($j$), where $i \in \{1, 2\}$ and $j \in \{1, 2\}$. The general form is represented as:
$A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}$
The given formula for the elements is $a_{ij} = \frac{(i+2j)^2}{2}$. We calculate each element individually:
Substituting the calculated values into the general $2 \times 2$ matrix structure:
$A = \begin{bmatrix} 4.5 & 12.5 \\ 8 & 18 \end{bmatrix}$
Final Solution: $A = \begin{bmatrix} 4.5 & 12.5 \\ 8 & 18 \end{bmatrix}$
Solution:
In matrix algebra, the dimension or order of a matrix is denoted by $m \times n$, where:
For any arbitrary matrix $A = [a_{ij}]_{m \times n}$, the element $a_{ij}$ occupies the position at the intersection of the $i$-th row and $j$-th column [Per the formal definition of matrix notation].
A matrix is classified as a square matrix if and only if the number of rows is exactly equal to the number of columns. This condition ensures that the matrix has an equal span in both dimensions, forming a geometric square in terms of its element distribution.
Given the general order $m \times n$:
By the definition of square matrices in linear algebra, the condition $m = n$ is the necessary and sufficient requirement for a matrix to be considered square. This implies that the matrix is an $n \times n$ matrix.
Final Solution: $m = n$
Solution:
A $3 \times 4$ matrix $A$ consists of $3$ rows and $4$ columns. The general representation of this matrix is:
$A = \begin{bmatrix} a_{11} & a_{12} & a_{13} & a_{14} \\ a_{21} & a_{22} & a_{23} & a_{24} \\ a_{31} & a_{32} & a_{33} & a_{34} \end{bmatrix}$
Each element $a_{ij}$ is determined by the mapping function $a_{ij} = \frac{1}{2}|-3i + j|$, where $i \in \{1, 2, 3\}$ and $j \in \{1, 2, 3, 4\}$.
We evaluate the elements row by row using the defined modulus function [Definition of Absolute Value: $|x| = x$ if $x \ge 0$, and $-x$ if $x < 0$].
| Row ($i$) | $j=1$ | $j=2$ | $j=3$ | $j=4$ |
|---|---|---|---|---|
| $i=1$ | $\frac{1}{2}|-3(1)+1| = 1$ | $\frac{1}{2}|-3(1)+2| = 0.5$ | $\frac{1}{2}|-3(1)+3| = 0$ | $\frac{1}{2}|-3(1)+4| = 0.5$ |
| $i=2$ | $\frac{1}{2}|-3(2)+1| = 2.5$ | $\frac{1}{2}|-3(2)+2| = 2$ | $\frac{1}{2}|-3(2)+3| = 1.5$ | $\frac{1}{2}|-3(2)+4| = 1$ |
| $i=3$ | $\frac{1}{2}|-3(3)+1| = 4$ | $\frac{1}{2}|-3(3)+2| = 3.5$ | $\frac{1}{2}|-3(3)+3| = 3$ | $\frac{1}{2}|-3(3)+4| = 2.5$ |
Substituting the calculated values into the matrix structure defined in Step 1:
$A = \begin{bmatrix} 1 & \frac{1}{2} & 0 & \frac{1}{2} \\ \frac{5}{2} & 2 & \frac{3}{2} & 1 \\ 4 & \frac{7}{2} & 3 & \frac{5}{2} \end{bmatrix}$
Final Solution: $A = \begin{bmatrix} 1 & 0.5 & 0 & 0.5 \\ 2.5 & 2 & 1.5 & 1 \\ 4 & 3.5 & 3 & 2.5 \end{bmatrix}$
Solution:
By the definition of equality of matrices, two matrices are equal if and only if their corresponding elements are identical [Per Definition of Matrix Equality]. Given the equation:
$\begin{bmatrix} a-b & 2a+c \\ 2a-b & 3c+d \end{bmatrix} = \begin{bmatrix} -1 & 5 \\ 0 & 13 \end{bmatrix}$
We equate the corresponding entries to form a system of four linear equations:
Utilizing Eq (i) and Eq (iii), we perform elimination [By Cramer’s Rule/Elimination Method]:
From Eq (iii), we isolate $b$: $b = 2a$.
Substitute $b = 2a$ into Eq (i):
$a - (2a) = -1$
$-a = -1 \implies a = 1$
Now, substitute $a = 1$ back into the expression for $b$:
$b = 2(1) = 2$
Substitute $a = 1$ into Eq (ii) to determine $c$:
$2(1) + c = 5$
$2 + c = 5 \implies c = 3$
Now, substitute $c = 3$ into Eq (iv) to determine $d$:
$3(3) + d = 13$
$9 + d = 13$
$d = 13 - 9 = 4$
| Variable | Value |
|---|---|
| $a$ | $1$ |
| $b$ | $2$ |
| $c$ | $3$ |
| $d$ | $4$ |
Final Solution: The values are $a=1, b=2, c=3, d=4$.