How Do You Calculate The Radius Of A Circle That's Circumference Is 56.548667772?

The formula for finding radius of a circle when the circumference of a circle is given is as follows:

Radius = C/2(π)
  where:
C  is the circumference of the circle
π  is Pi, approximately 3.142  
Thus putting in the values we get
Radius = 56.548667772/2(3.142)
           = 8.9988
Thus the answer is approximately 8.9988

While the answer given has all the right elements it will not yield the correct answer if calculated as stated. C/2(n) actually equals 88.8379571. It is very important to make sure that the brackets are in the right place otherwise the answer will be wrong. Any dependant calculation can only be completed correctly once the precedent calculations (any in brackets) have been completed. A less ambiguous phrasing could be shown thus: R=C/(2xn). This gives the result of 8.99883319 as suggested.

How do you calculate the radius of a circle thats circumference is 100mm

I think you multiply that by 3.14

Using the well known formula:
2πr = the circumference ........(r is the radius of the circle)

Therefore:                                                                                  

2πr = 56.548667772;

2r = 56.548667772/π;
2r = 17.99999999999999999999;
so rounding up:
2r = 18;
r = 9;

(The radius of the circle is 9)