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Example 2-5e Objective Find the circumference and area of circles

Example 2-5e Vocabulary Circle A set of all points in a plane that are the same distance from a given point called the center

Example 2-5e Vocabulary Center The given point from which all points on a circle are the same distance

Example 2-5e Vocabulary Radius The distance from the center of a circle to any point on the circle

Example 2-5e Vocabulary Diameter The distance across a circle through its center

Example 2-5e Vocabulary Circumference The distance around a circle

Example 2-5e Vocabulary pi The ratio of the circumference of a circle to its diameter Pi = 3.14 

Lesson 2 Contents Example 1Find the Circumferences of Circles Example 2Find the Circumferences of Circles Example 3Find the Areas of Circles Example 4Find the Areas of Circles

Example 2-1a Find the circumference of the circle. Round to the nearest hundredth. Write formula for circumference Replace d with 5 C = feet Multiply Answer: C = feet 1/4 Add dimensional analysis

Example 2-1b Find the circumference of the circle. Round to the nearest hundredth. Answer: C = inches 1/4

Example 2-2a Find the circumference of the circle. Round to the nearest hundredth. Answer: C = /4 Write formula for circumference Remember: If given radius then double it for the diameter Replace d with 5 D = 3.8  2 C =   7.6 Multiply Add dimensional analysis meters

Example 2-2b Find the circumference of the circle. Round to the nearest hundredth. Answer: C = meters 2/4

Example 2-3a Find the area of the circle. Round to the nearest hundredth. Write formula for area of a circle Replace r with 3 3/4 Follow Order of Operations P E MD AS Evaluate 3 2

Example 2-3a Find the area of the circle. Round to the nearest hundredth. Multiply Answer: A = /4 Add dimensional analysis yards 2

Example 2-3b Find the area of the circle. Round to the nearest hundredth. Answer: A = feet 2 3/4

Example 2-4a Find the area of the circle. Round to the nearest hundredth. 4/4 Write formula for area of a circle Replace r with 5 Remember: If given the diameter, divide by 2 R = 10  2

Example 2-4a Find the area of the circle. Round to the nearest hundredth. Answer: A = /4 Follow Order of Operations P E MD AS Evaluate 5 2 Multiply Add dimensional analysis inches 2

Example 2-4b Find the area of the circle. Round to the nearest hundredth. Answer: centimeters 2 4/4

End of Lesson 2 Lesson 7:2Circumference and Area of Circles All Assignment

Example 2-5a POOLS The Patels have a circular pool with a radius of 12 feet. They plan on installing a 4-foot-wide walkway around the pool. What will be the area of the walkway? To determine the area of the walkway, you must subtract the area of the pool from the area of the outer circle that includes the pool and the walkway. 5/5

Example 2-5b Area of Outer Circle Area of a circle Multiply Replace r with 12 4 or 16. Evaluate A = /5

Example 2-5c Area of Pool Area of a circle Multiply Replace r with 12. Evaluate A = /5

Example 2-5d Area of Walkway Area of Outer Circle – Area of Pool Answer: The area of the walkway is feet /5

Example 2-5e GARDENS The Shoemakers have a circular pond with a radius of 4 feet. They plan on installing a 2-foot-wide walkway around the pond. What will be the area of the walkway? Answer: Area of walkway is ft 2 * 5/5