1. Circumference and Area of a Circle
Chapter 8
Section 8.5

2. Objective
The students will be able to find the circumference and area of a circle.

3. Vocabulary Circumference – is the distance around a circle
Pi – the ratio of a circle’s diameter to its circumference noted by the symbol 𝜋

4. Concept 𝑇ℎ𝑒 𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑜𝑓 𝑎 𝑐𝑖𝑟𝑐𝑙𝑒 𝑖𝑠 𝜋 𝑡𝑖𝑚𝑒𝑠 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟.
𝐶=𝜋∙𝑑 𝑜𝑟 𝐶=2𝜋∙𝑟. d r

5. Example
Find the area to the nearest tenth of a unit.
5 ft
13 m

6. Concept
𝑇ℎ𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑎 𝑐𝑖𝑟𝑐𝑙𝑒 𝑖𝑠 𝑡ℎ𝑒 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝜋 𝑎𝑛𝑑 𝑡ℎ𝑒 𝑠𝑞𝑢𝑎𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑎𝑑𝑖𝑢𝑠 𝑟.
𝐴=𝜋 𝑟 2
𝑟𝑒𝑚𝑒𝑚𝑏𝑒𝑟 𝑟 2 =𝑟∙𝑟 r

7. Example
Find the area to nearest unit.
9 m
12 m

8. Questions?

9. Exit Ticket
Find the circumference and area to the nearest tenth of a unit.
15 yd

10. Worksheet