Circumference and Area of a Circle Chapter 8 Section 8.5

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

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

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

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

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

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

Questions?

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

Worksheet