The formula of the circumference of a circle is:
C = 2 π r
Since r is not given, I will use all choices to find the radius. Whatever circumference corresponds to the correct radius of the problem, then it is the correct one.
a) 22.0 cm = 2 3.14 r ⇒ r = 22.0 cm / 6.28 ⇒ r = 3.50 cm
b) 69.1 cm = 2 3.14 r ⇒ r = 69.1 cm / 6.28 ⇒ r = 11.00 cm
c) 34.5 cm = 2 3.14 r ⇒ r = 34.5 cm / 6.28 ⇒ r = 5.49 cm
d) 17.3 cm = 2 3.14 r ⇒ r = 17.3 cm / 6.28 ⇒ r = 2.75 cm
