Question

Let $A$ be the $2\times 2$ matrices given by $A=\left[a_{ij}\right]$ where $a_{ij}\in \{0,1,2,3,4\}$. Such that $a_{11}+a_{12}+a_{21}+a_{22}=4$.
The number of matrices $A$ such that $A$ is invertible are

• A. 18
• B. 19
• C. 20
• D. 12

Answer 1

Answer: (A)

Correct answer is (a) 18