The answer is 7/40.
To solve, you have to find the LCM (least common denominator) for 5/8 and 4/5. 5/8= 25/40 and 4/5= 32/40. Subtract and you get 7/40. That is your answer.
The circumference is the diameter multiplied by pi, and the radius is half of the diameter. If we divide 241.37 by pi we get a diameter of 77, and half of that is the radius, which is 38.5.