1. Lesson 20.1 Justifying Circumference and area of a circle
Please tear out pages

2. Circumference & Area of a Circle
𝑅𝑎𝑑𝑖𝑢𝑠=𝑟
𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟=2𝑟
𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒=2𝜋𝑟 or 𝜋𝑑
𝐴𝑟𝑒𝑎=𝜋 𝑟 2

3. Example 1 – Find the circumference and area of each circle with the given radius or diameter. Round to the nearest tenth. Use 3.14 for 𝜋.
𝑎) 𝑟=14 𝑐𝑚
𝑏) 𝑑=24 𝑓𝑡
𝐶=2𝜋𝑟
𝐶=𝜋𝑑
𝐶=2(3.14)(14)
𝐶=(3.14)(24)
𝐶=28(3.14)
𝐶=75.36 𝑓𝑒𝑒𝑡
𝐶=28(3.14)
𝐴=𝜋 (12) 2
𝐶=87.92 𝑐𝑚
𝐴=(3.14)(144)
𝐴=𝜋 𝑟 2
𝐴= 𝑓𝑡 2
𝐴=(3.14) (14) 2 𝐴=
𝐴= 𝑐𝑚 2

4. Assignment #
Pg. 1082
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