Question:
Two sides of a parallelogram are in the ratio 5 : 3. If its perimeter is 64 cm, find the lengths of its sides.
Solution:
Let the lengths of two sides of the parallelogram be $5 x \mathrm{~cm}$ and $3 x \mathrm{~cm}$, respectively.
Then, its perimeter $=2(5 x+3 x) \mathrm{cm}$
$=16 x \mathrm{~cm}$
$\therefore 16 x=64$
$\Rightarrow x=\frac{64}{16}$
$\Rightarrow x=4$
Other side $\Rightarrow(3 \times 4) \mathrm{cm}=12 \mathrm{~cm}$