What will be the number of unit squares

Let the numbor $5 e x$. Then, number of unit squares $=x \times x=x^{2}$

But total number of unit squares $=256$

$\therefore$ $x^{2}=256$

$\Rightarrow$ $x=\sqrt{256}=\sqrt{16 \times 16}=16$

Hence, the required number of squares is 16 .