# NCERT Class 12-Mathematics: Exemplar Chapter –3 Matrices Part 21

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**Question 59:**

If matrix , where if then is equal to

(A) I

(B) A

(C) 0

(D) None of these

**Answer: (A)**

**Question 60:**

The matrix is a

(A) Identity matrix

(B) Symmetric matrix

(C) Skew symmetric matrix

(D) None of these

**Answer: (B)**

**Question 61:**

The matrix is a

(A) Diagonal matrix

(B) Symmetric matrix

(C) Skew symmetric matrix

(D) Scalar matrix

**Answer: (C)**

**Question 62:**

If A is matrix of order and B is a matrix such that AB′ and B′A are both defined, then order of matrix B is

(A)

(B)

(C)

(D)

**Answer: (D)**

**Question 63:**

If A and B are matrices of same order, then is a

(A) Skew symmetric matrix

(B) Null matrix

(C) Symmetric matrix

(D) Unit matrix

**Answer: (A)**

**Question 64:**

If A is a square matrix such that , then is equal to

(A)

(B)

(C)

(D)

**Answer: (A)**

**Question 65:**

For any two matrices A and B, we have

(A)

(B)

(C)

(D) None of the above

**Answer: (D)**

**Question 66:**

On using elementary column operations in the following matrix equation

we have:

(A)

(B)

(C)

(D)

**Answer: (D)**

**Question 67:**

On using elementary row operation in the following matrix equation:

, we have:

(A)

(B)

(C)

(D)

**Answer: (A)**