Question

Let A = $\left[\begin{array}{cc}1& 6\\ 2& 5\end{array}\right]$, B = $\left[\begin{array}{cc}3& 4\\ 4& 9\end{array}\right]$ then find sum of diagonal elements of A + B.

• A. 18

Answer 1

The correct option is A 18

We know that when we add two matrices say A&B, A+B, the resultant matrix will have elements which are sum of corresponding elements of A&B.

So $\left[\begin{array}{cc}1& 6\\ 2& 5\end{array}\right]$ + $\left[\begin{array}{cc}3& 4\\ 4& 9\end{array}\right]$

= $\left[\begin{array}{cccccc}1& +& 3& 6& +& 4\\ 2& +& 4& 5& +& 9\end{array}\right]$

= $\left[\begin{array}{cc}4& 10\\ 6& 14\end{array}\right]$
Diagonal elements are 4 and 14
Sum = 4 + 14 = 18