Question 573020
You have to be more specific with what 16cm, 20cm, etc are.  Are those radii or diameters?


The formula for circumference is
C =  pi x diameter
The formula for area of a circle is
A = pi x radius^2
Finally,
diameter = radius x 2



With those three formulas, you should be able to solve this for each of the lengths you mention, being careful to convert radius and diameter.


Good luck!!