1. 17.59
2. 81.68
3. 8.99225
4. 12.00028
Step-by-step explanation:
for the first two you have to multiply the radii by 2 to find the diameter, then multiply your diameter by pi (3.14) to find the circumference
for the second two you have to work backwards so you have to divide the circumference by pi (3.14) which will give you the diameter, then you have to divide the diameter by 2 to get the radius.