Let's take the ratio of a standard square of side 4. What is the ratio

r = (p^2)/a?

To take the perimeter of a square we add up all the sides. Since the sides of a square are all the same we have 4 x (s) where s signifies the measurement of one side.

The area of a square is side x side or s^2.....

and perimeter squared = (4s)^2

so r=(4s)^2/s^2


cancelling we get 16....Ta Da...