Question

$A=\left[\begin{array}{ccc}1& 2& 3\\ 2& 3& 1\\ 3& 1& 2\end{array}\right]andB=\left[\begin{array}{c}14\\ 11\\ 11\end{array}\right]$
Find the order of a matrix X such that A.X = B

• A. $3\times 3$
• B. $1\times 3$
• C. $3\times 1$
• D. $1\times 1$

Answer 1

The correct option is C

$3\times 1$

Let the order of matrix X be $a\times b$
Given A.X=B
$={\left[\begin{array}{ccc}1& 2& 3\\ 2& 3& 1\\ 3& 1& 2\end{array}\right]}_{3\times 3}{X}_{a\times b}={\left[\begin{array}{c}14\\ 11\\ 11\end{array}\right]}_{3\times 1}$

Therefore order of matrix X is $3\times 1$