Circumference = PI x diameter
FInd the diamter:
19.5 = 3.14 x diameter
Divide both sides by 3.14:
Diameter = 19.5 / 3.14
Diameter = 6.21019108 inches.
Radius = diameter / 2
Radius = 6.21019108 / 2
Radius = 3.10509554 inches
Rounded to the nearest hundredth = 3.11 inches.