I've measured mine for you, it was ten and a half inches or 26.7cm
4 pi inches
The the center of the donut , more specifically the center of the hole of the donut. Considering the donut is perfectly symmetrical we only need to look at the geometric center of it , same applies for a hollow sphere like a soccer ball ,the center is indeed in the middle where there is no mass.
You may be able to get a donut from Saturn of Tampa, or you could possibly get a donut from a used tire store.
The formula; 2 * Pi * Radius = circumference Will calculate the circumference of a circle.
Pi X D = Circumference. To find Diamater if you know Circumference, divide Circumference by Pi (3.14).
Diameter = Circumference/pi
Circumference = π * Diameter
You divide the circumference by pi.
diameter = circumference/pi
If you know the circumference of a circle, you can find the radius by dividing the circumference by the value of Pi (3.14159...)
You cannot find the diameter of something from its circumference unless it is a circle and, in that case, diameter = circumference/pi
Divide the circumference by Pi to find the diameter.