Question

# If a matrix has 13 elements, then the possible dimensions (orders) of the matrix are (a) $13\times 1\text{ or }1\times 13$ (b) $1\times 26\text{ or 26}\times \text{1}$ (c) $2\times 13\text{ or 13}\times \text{2}$ (d) $13\times 13$

Now, we let the dimension of the matrix be $x\times y$ . So, according to the above constraints, we can say that x, y are non-negative integers, and $xy=13$ .
Now, there are only two sets (x,y) satisfying the condition mentioned above: (13,1) and (1,13). So, the dimensions of the matrix can be $13\times 1\text{ or }1\times 13$ .