Matrix Operations: Step-By-Step Multiplication Example

7. Example:

   $AB = \begin{bmatrix}1 & 2 \\ \boldsymbol{\color{green}{3}} & \boldsymbol{\color{green}{4}} \\ 5 & 6 \\ 7 & 8\end{bmatrix} \begin{bmatrix}\boldsymbol{\color{green}{1}} & 0 & 2 \\ \boldsymbol{\color{green}{0}} & 1 & 3\end{bmatrix} = \begin{bmatrix} 1 & 2 & 8 \\ \boldsymbol{\color{green}{3}} & c_{2,2} & c_{2,3}\\ c_{3,1} & c_{3,2} & c_{3,3}\\ c_{4,1} & c_{4,2} & c_{4,3} \end{bmatrix} = C$

   
   Explanation: We do $c_{2,1} =$$\; 3 \cdot 1 + 4 \cdot 0 =$$\; 3 + 0 =$$\; 3$. This is the element on row $2$ and column $1$, so we used row $2$ of matrix $A$ and column $1$ of matrix $B$.