If the diagonals of a rhombus are 12 cm and 16cm,

All sides of a rhombus are equal in length.

The diagonals intersect at $90^{\circ}$ and the sides of the rhombus form right triangles.

One leg of these right triangles is equal to $8 \mathrm{~cm}$ and the other is equal to $6 \mathrm{~cm}$.

The sides of the triangle form the hypotenuse of these right triangles.

So, we get:

$\left(8^{2}+6^{2}\right) \mathrm{cm}^{2}$

$=(64+36) \mathrm{cm}^{2}$

$=100 \mathrm{~cm}^{2}$

The hypotneuse is the square root of $100 \mathrm{~cm}^{2}$. This makes the hypotneuse equal to 10 . T

hus, the side of the rhombus is equal to $10 \mathrm{~cm}$.