Class CBSE Class 12 Mathematics Matrices and Determinants Q #841
KNOWLEDGE BASED
APPLY
1 Marks 2023 MCQ SINGLE
1. If $x\begin{bmatrix}1\\ 2\end{bmatrix}+y\begin{bmatrix}2\\ 5\end{bmatrix}=\begin{bmatrix}4\\ 9\end{bmatrix}$, then
(A) $x=1, y=2$
(B) $x=2, y=1$
(C) $x=1, y=-1$
(D) $x=3, y=2$

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Step-by-Step Solution

The given equation is: $x\begin{bmatrix}1\\ 2\end{bmatrix}+y\begin{bmatrix}2\\ 5\end{bmatrix}=\begin{bmatrix}4\\ 9\end{bmatrix}$

Performing scalar multiplication, we get: $\begin{bmatrix}x\\ 2x\end{bmatrix}+\begin{bmatrix}2y\\ 5y\end{bmatrix}=\begin{bmatrix}4\\ 9\end{bmatrix}$

Adding the matrices, we have: $\begin{bmatrix}x+2y\\ 2x+5y\end{bmatrix}=\begin{bmatrix}4\\ 9\end{bmatrix}$

Equating the corresponding elements, we get the following system of linear equations:

1) $x + 2y = 4$

2) $2x + 5y = 9$

We can solve this system of equations using substitution or elimination. Let's use elimination.

Multiply equation (1) by 2: $2x + 4y = 8$

Subtract this new equation from equation (2): $(2x + 5y) - (2x + 4y) = 9 - 8$

This simplifies to: $y = 1$

Substitute $y = 1$ into equation (1): $x + 2(1) = 4$

So, $x + 2 = 4$, which gives $x = 2$

Correct Answer: x=2, y=1

AI Suggestion: Option B

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to apply their knowledge of matrix operations and solving systems of linear equations to find the values of x and y.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure to solve the problem, which involves performing scalar multiplication, matrix addition, and solving a system of linear equations.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly tests the student's understanding and application of concepts related to matrices and linear equations as covered in the textbook.