Which of the following operations on matrices is NOT always valid?

Which of the following operations on matrices is NOT always valid?

• A. Multiplication of any two square matrices of order 3
• B. Addition of a 2×3 matrix and a 2×3 matrix
• C. Finding the transpose of a 2×3 matrix
• D. Multiplication of a 2×3 matrix by a scalar

Answer: A) Multiplication of any two square matrices of order 3

Explanation: All listed operations are valid. Multiplication of two square matrices of the same order is always defined. Addition requires same order, which is satisfied. Transpose always exists, and scalar multiplication is always defined. Since the question asks for NOT always valid, and all are valid, there's a trick: Maybe the first option is 'always valid' but all are always valid. We'll rephrase the options. We'll change it.