Question Bank • QB_EXP_EM_MAT_004 MCQ • 1 Mark

Section 1: Engineering Mathematics

Linear Algebra: Matrices & Determinants

Subtopic: Determinant properties

Question Statement:

Let $A$ be a $3 \times 3$ real matrix with $\det(A) = 6$. The determinant of the scalar multiplied matrix $5A$ is:

Options:

  • (A) 750
  • (B) 30
  • (C) 150
  • (D) 3750

Answer Key:

A

Step-by-Step Solution & Explanation

For any $n \times n$ square matrix $A$ and a scalar $k$, the determinant scaling property states that: $\det(k A) = k^n \det(A)$ Given that $n = 3$, $k = 5$, and $\det(A) = 6$: $\det(5A) = 5^3 \times 6 = 125 \times 6 = 750$ Hence, the correct determinant value is $750$.
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