Find the radius of a circle whose circumference is 68 inches

To get the radius from the circumference, you must first find the diameter. 
(Radius=Half of the circle, inside width)
(Diameter= The entire width of the inside of the circle)
(Circumference= the length of the outer ring of the circle)
How to calculate:
Radius *2=Diameter
Diameter* Pi= circumference
Circumference/Pi=Diameter
Diameter/2=Radius

So, we take 68, and divide it by the first 3 digits of Pi, with is 3.14
We get a number that can be rounded 1 hundredth up to 21.65
Take that number (which now represents the diameter) and divide it by 2 in order to get the radius. 21.65/2=10.825
You can round that off to either 10.8, or 10.83
~Hope this helps!