Geometry Worksheet
8.9 – Circumference of Circles
Name ____________________________________
1. What is the relationship between the radius and the diameter?_________________________________________
2. If the radius is 5cm, then the diameter is __________
3. If the diameter is 14cm, then the radius is _________
4. If the radius is 3.5in, then the diameter is __________
5. If the diameter is 11ft, then the radius is __________
Find the radius and the diameter of each circle. Include proper units!
6.
7.
8.
9.
Radius = ________ Diameter = ________
Radius = ________ Diameter = ________
Radius = ________ Diameter = ________
Radius = ________ Diameter = ________
10. What is the FORMULA for CIRCUMFERENCE of a circle? _______________
EXACT:
Use the  symbol – NOT 3.14
APPROX:
Use 3.14 – NOT the  symbol or the key
Find the EXACT and APRROXIMATE circumference of each circle. Your answers should have plain units!
11.
12.
13.
14.
Radius = ________ Diameter = ________ Radius = ________ Diameter = ________
Radius = ________ Diameter = ________
Radius = ________ Diameter = ________
EXACT Circumference _______________
EXACT Circumference _______________
EXACT Circumference _______________
EXACT Circumference ________
APPROX. Circumference _______________
APPROX. Circumference _______________
APPROX. Circumference _______________
APPROX. Circumference_______
15. Radius = 13cm
16. Radius = 7in
17. Diameter = 6ft
18. Diameter = 16mm
EXACT Circumference _______________
EXACT Circumference _______________
EXACT Circumference _______________
EXACT Circumference ________
APPROX. Circumference _______________
APPROX. Circumference _______________
APPROX. Circumference _______________
APPROX. Circumference_______
Given the CIRCUMFERENCE, WORK BACKWARDS using the formula to find the radius.
19. Circum = 20 cm.
20. Circum = 10 in.
21. Circum = 94.2 ft.
22. Circum = 15.70 cm.
Radius = ________
Radius = ________
Radius = ________
Radius = ________
23. Find the approximate circumference of a circle with
diameter = 10cm
24. Find the approximate circumference of a circle with
radius = 5cm
25. Find the exact circumference of a circle with radius =
3cm
26. Find the exact circumference of a circle with diameter =
12cm
27. State the FORMULA for finding ARC LENGTH:
Use the formula to find each arc length.
28.
29.
30.
31.
d = _____
d = _____
d = _____
d = _____
Circumference ________
Circumference ________
Circumference ______________
Circumference ______
Fraction of circle highlighted _______
Fraction of circle highlighted _______
Fraction of circle highlighted _______
Fraction of circle highlighted ___
Arc Length _______
Arc Length _______
Arc Length _______
Arc Length _______
32. The Ferris Wheel has a radius of 18ft.
A. What is the diameter? _____________
B. Calculate the approximate circumference. ______________
C. If there are nine chairs on the ferris wheel, what is the arc length between each chair? ______________
33. A birthday cake is sliced into 8 equal pieces. The arc length of one piece of cake is 6.28 inches as shown.
Find the diameter of the cake.