# 2.4 Multiplication of a Matrix by a Number

2.4 Multiplication of a Matrix by a Number
When matrix is multiplied by a number, every element in the matrix is multiplied by the number.

Example:
Given that  $A=\left(\begin{array}{cc}-2& 4\\ 5& -6\end{array}\right)$ , find each of the following.
(a) 3A
(b) -2A

Solution:
$\begin{array}{l}\text{(a)}3A=3\left(\begin{array}{cc}-2& 4\\ 5& -6\end{array}\right)\\ =\left(\begin{array}{cc}3×\left(-2\right)& 3×4\\ 3×5& 3×\left(-6\right)\end{array}\right)\\ =\left(\begin{array}{cc}-6& 12\\ 15& -18\end{array}\right)\end{array}$

### 2 thoughts on “2.4 Multiplication of a Matrix by a Number”

1. Hi, For example (b) -2A. There is a mistake where -2 x -2 should be 4 not -4. Please recitfy.

• Dear Gurdit Singh,