Question 4 - CBSE Class 12 Sample Paper for 2026 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards

Last updated at August 10, 2026 by Teachoo

[MCQ] If 𝐴 is a square matrix of order 4 and |𝑎𝑑𝑗 𝐴|=27, then 𝐴 - CBSE Class 12 Sample Paper for 2026 Boards

part 2 - Question 4 - CBSE Class 12 Sample Paper for 2026 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12

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Question 4 If 𝐴 is a square matrix of order 4 and |adj 𝐴|=27, then 𝐴(adj 𝐴) is equal to (A) 3 (B) 9 (C) 3𝐼 (D) 9𝐼We know that 𝑨.( adj 𝑨)=|𝑨|𝑰 Finding |A| Our formula is |adj (A)| = |A|n − 1 Where n is the order of matrix Since A is of order 4, therefore n = 4 Thus, |adj (A)| = |A|4− 1 27 = |A|3 |A|3 = 27 |A|3 = 33 |A| = 3 Now, 𝐴.( adj 𝐴)=|𝐴|𝐼 Putting |A| = 3 𝑨.( adj 𝑨)=𝟑𝑰 So, the correct answer is (C) Note: 𝑨.( adj 𝑨) gives a matrix, not a number. So, 3I is correct

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