Circumference is Pi x d
so it is 55 Pi which is roughly 172.7 cm
If that's the diameter, you can multiply that by pi (which is approximately 3.14), to get the circumference.
The diameter of a circle that has a 33 cm circumference is: 10.5 cm (circumference divided by pi = diameter).
The diameter is 23.99 cm (circumference divided by Pi = diameter).
The circumference of circle that is 8 cm is: about 25.13 cm (diameter x pi = circumference).
If the circumference is 20 cm then the diameter is 6.366 cm