Class CBSE Class 12 Mathematics Matrices and Determinants Q #1680
COMPETENCY BASED
APPLY
1 Marks 2026 AISSCE(Board Exam) MCQ SINGLE
If $A=[a_{ij}]$ is a $2\times 2$ matrix whose elements are given by $a_{ij}=\frac{|i-3j|}{2}$, then $A^{\prime}$ is:
(A) $\begin{bmatrix}1&\frac{5}{2}\\\frac{1}{2}&2\end{bmatrix}$
(B) $\begin{bmatrix}1&\frac{1}{2}\\\frac{5}{2}&2\end{bmatrix}$
(C) $\begin{bmatrix}2&\frac{5}{2}\\\frac{1}{2}&1\end{bmatrix}$
(D) $\begin{bmatrix}2&\frac{1}{2}\\\frac{5}{2}&1\end{bmatrix}$
Correct Answer: B

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Detailed Solution

Step 1: Define the matrix elements

The matrix $A$ is a $2 \times 2$ matrix, so it has elements $a_{11}, a_{12}, a_{21}, a_{22}$. We use the formula $a_{ij} = \frac{|i-3j|}{2}$ to calculate each:

For $i=1, j=1$: $a_{11} = \frac{|1-3(1)|}{2} = \frac{|-2|}{2} = 1$

For $i=1, j=2$: $a_{12} = \frac{|1-3(2)|}{2} = \frac{|-5|}{2} = \frac{5}{2}$

For $i=2, j=1$: $a_{21} = \frac{|2-3(1)|}{2} = \frac{|-1|}{2} = \frac{1}{2}$

For $i=2, j=2$: $a_{22} = \frac{|2-3(2)|}{2} = \frac{|-4|}{2} = 2$

Step 2: Construct matrix A

Substituting the calculated values into the matrix form:

$$A = \begin{bmatrix} 1 & \frac{5}{2} \\ \frac{1}{2} & 2 \end{bmatrix}$$

Step 3: Find the transpose A'

The transpose $A'$ is obtained by swapping rows and columns:

$$A' = \begin{bmatrix} 1 & \frac{1}{2} \\ \frac{5}{2} & 2 \end{bmatrix}$$

Final Answer: Option (B)

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must apply the definition of matrix construction and the operation of matrix transposition to solve a multi-step problem.
Knowledge Dimension: PROCEDURAL
Justification: The question requires following a specific algorithmic sequence: calculating individual elements based on a formula and then performing a matrix transformation.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. It tests the foundational understanding of matrix algebra as prescribed in the NCERT curriculum for Matrices.