1. DO NOW
Complete number 6
(Area and Perimeter)
on sheet 6-8

2. Circles and circumference Objective: Find the circumference of circles
Chapter 6 lesson 9
Circles and circumference
Objective: Find the circumference of circles

3. Show Brain Pop Video

4. Vocabulary
Circle:
the set of all points in a plane that are the same distance from a given point called the center.
center

5. Vocabulary
Radius: r
The distance from the center to any point on a circle.
Circumference: C
The distance around the circle
Diameter: d
The distance across a circle through the center

6. Pi …
Where has Pi come from?

7. Pi: The ratio of the circumference of a circle to its diameter.
The circumference is 3.14… times the diameter. d

8. The circumference of a circle
C = d or
C = 2 r

9. To solve each problem make sure you solve using the 4 steps!
F: Formula
P: Plug it in
S: Solve
A: Answer

10. Lets try some C = 2 x 3.14 x 8 C = 16 x 3.14 C = 50.24 C= 50.2 ft
Find the circumference of each circle. Round to the nearest tenth if necessary.
C = d or C = 2 r
8 ft
C = 2 x x 8
C = 16 x 3.14
C = 50.24
C= 50.2 ft

11. Lets try some
Find the circumference of each circle. Round to the nearest tenth if necessary.
C = d or C = 2 r
14 m
C = x 14
C = 43.96
C = 44 m

12. Leave your answer in terms of pi.
Lets try some more!!
Find the circumference of each circle.
Leave your answer in terms of pi.
C = d or C = 2 r
C = 2 x x 11.7
C = 23.4 x
C = cm
Radius = 11.7 cm

13. Leave your answer in terms of pi.
Lets try some
Find the circumference of each circle.
Leave your answer in terms of pi.
C = d or C = 2 r
C = x 3.5
C = yd
diameter = 3 ½ yd

14. Turn to page 276 in your textbooks
Do numbers 11 and 12 ( solve out answer)
And
Numbers 13 and 15 (answer in terms of pi)