If a matrix has 18 elements, what are the possible orders it can have?

Number of entries $=$ (Number of rows) $\times$ (Number of columns) $=18$

If order is $(a \times b)$ then, Number of entries $=a \times b$

So now $\mathrm{a} \times \mathrm{b}=18$ (in this case)

Possible cases are $(1 \times 18),(2 \times 9),(3 \times 6),(6 \times 3),(9 \times 2),(18 \times 1)$

Conclusion: If a matrix has 18 elements, then possible orders are $(1 \times 18),(2 \times 9),(3 \times 6),(6 \times 3),(9 \times 2),(18 \times 1)$