Question

$\left[\begin{array}{ccc}1& 0& 2\\ -1& 1& -2\\ 0& 2& 1\end{array}\right]+\left[\begin{array}{ccc}5& 1& -2\\ 1& 1& 0\\ -2& -2& 1\end{array}\right]$

What will be the sum of the diagonal elements of the resultant matrix?

• A. 10
• B. 6
• C. 9
• D. 7

Answer 1

The correct option is A 10

$\left[\begin{array}{ccc}1& 0& 2\\ -1& 1& -2\\ 0& 2& 1\end{array}\right]+\left[\begin{array}{ccc}5& 1& -2\\ 1& 1& 0\\ -2& -2& 1\end{array}\right]=\left[\begin{array}{ccc}6& 1& 0\\ 0& 2& -2\\ -2& 0& 2\end{array}\right]$

Sum of diagonal $=6+2+2=10$