CIRCUMFERENCE
#9
Circumference is the perimeter of a circle, that is, the distance around the circle.
d = diameter
r = radius
! " 3.14
C = πd or C = 2πr
Example 1
Example 2
Example 3
Find the circumference of a
circle with a diameter of
15 inches.
Find the circumference of a
circle with a radius of
12 units.
Find the diameter of a circle
with a circumference of
254.34 inches.
r = 12, so d = 2(12) = 24
C =πd
254.34 = π d
254.34 = 3.14d
d = 15 inches
C =πd
= π(15) or 3.14(15)
= 47.1 inches
C = 3.14(24)
= 75.36 units
254.34
d = 3.14 = 81 inches
Problems
Find the circumference of each circle given the following diameter or radius lengths. Round
your answer to the nearest hundredth. Use π = 3.14.
1.
d = 53 ft
2.
d = 8.5 ft
3.
r = 7.3 m
4.
d = 63 m
5.
r = 2.12 cm
Find the circumference of each circle shown below. Round your answer to the nearest
hundredth. Use π = 3.14.
6.
7.
11 yds
•
52 mm
Find the diameter of each circle given the circumference. Round your answer to the nearest
tenth. Use π = 3.14.
8.
C = 54.636 mm
9.
C = 135.02 km
10.
C = 389.36 km
Answers
1.
5.
9.
166.42 ft
13.31 cm
43 km
2.
6.
10.
26.69 ft
69.08 yds
124 km
© 2011 CPM Educational Program. All rights reserved.
3.
7.
45.84 m
163.28 mm
4.
8.
197.82 m
17.4 mm