Question

10. Given matrices A, B, and C below, perform the indicated operations if possible. If the operation is not possible, explain why.

Answer 1

Answer(a):

Order of matrix A = 3x3 {because number of rows=3, number of columns=3}

Order of matrix B = 3x3

Order of matrix C = 1x3

3A will be of order 3x3 because multiply by scalar doesn't change the order. Which is same as the order of matrix B.

So 3A+B is possible.

We simply multiply all elements of A with 3 and add them with corresponding elements of B.

$3\begin{bmatrix}2 & -1& 0\\ 0 & 5& 0.3\\ 1 & 4&10 \end{bmatrix}+\begin{bmatrix}5 & 0& 2\\ 1 & -3& 9\\ 2 & 0& 4\end{bmatrix}= \begin{bmatrix}11 & -3& 2\\ 1 & 12& 9.9\\ 5 & 12& 34\end{bmatrix}$

Answer(b):

2B will be of order 3x3 because multiply by scalar doesn't change the order. Which is NOT same as the order of matrix C.

So 2B+C is NOT possible.

Answer(c):

CA is possible only if

number of columns of C = number of columns of A

3=3

which is true hence CA is possible.

$\begin{bmatrix}1 &3 &5 \end{bmatrix}*\begin{bmatrix}2 & -1& 0\\ 0 & 5& 0.3\\ 1 & 4&10 \end{bmatrix}=\begin{bmatrix}1*2+3*0+5*1 & 1*-1+3*5+5*4 & 1*0+3*0.3+5*10\end{bmatrix}$

= $\begin{bmatrix}7 & 34& 50.9\end{bmatrix}$

If the matrix is not visible properly then look at the attached picture.