Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

If A is a square matrix of order 3 and |A| = 5, then |adj(adj A)| is:

Options:

125

625

75

375

Correct Answer:

625

Explanation:

The correct answer is Option (2) - 625

$\text{For an } n \times n \text{ matrix: } |\text{adj } A| = |A|^{n-1}$

$|\text{adj}(\text{adj } A)| = |\text{adj } A|^{n-1}$

$n = 3,\;\; |A| = 5$

$|\text{adj } A| = 5^{3-1} = 5^2 = 25$

$|\text{adj}(\text{adj } A)| = 25^{3-1} = 25^2 = 625$

$|\text{adj}(\text{adj } A)| = 625$