1. Circumference & Area

2. Parts of a Circle
d = 2r
and
diameter 1
r= d
2
radius

3. Circumference
(Distance around a circle)
8 in. π = 3.14 4 in.
C= π d or C=2π r
C = 3.14(8) C = 2(3.14)(4)
C = 25.12 in. C = 25.12 in

4. Give it a try!
1. If the diameter is 10 feet, what is the
radius?
2. If the radius is 3.2 inches, what is the
diameter?
3. Find the circumference: 15 cm
3 mm
4. Find the circumference:

5. Give it a try!
1. If the diameter is 10 feet, what is the
radius? r = 5 feet
2. If the radius is 3.2 inches, what is the
diameter? d = 6.4 in.
3. Find the circumference: 15 cm
C = 3.14 x 15 = 47.1 cm
4.Find the circumference: 3 mm
C = 2 x 3.14 x 3 = 18.84 mm

6. Area of a Circle
(The inside of the circle)
3m d = 10 in
10 in π
r = 5 in
A= πr 2
2
A= πr)
A = 3.14(5
2
2
A = 3.14(3 ) 2
A = 28.26 m
2 A = 78.5 in

7. You try!
7 in 20 ft.
A= πr 2

8. You try!
20 ft.
7 in
d = 20, so r =
π π
2
A= r 10
2
2
A = 3.14(7 ) A= r2
2
2
A = 153.86 in A = 3.14(10 )
A = 314 ft