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Example 6-2b Objective Find the circumference of circles

Example 6-2b Vocabulary Circle The set of all points in a plane that are the same distance from a point called the center

Example 6-2b Vocabulary Center The point the same distance from all points of a circle

Example 6-2b Vocabulary Diameter The distance across a circle through the center

Example 6-2b Vocabulary Circumference The distance around a circle

Example 6-2b Vocabulary Radius The distance from the center to any point on a circle

Example 6-2b Math Symbols = 3.14 called pi

Lesson 6 Contents Example 1Find the Circumference of a Circle Example 2Use Circumference to Solve a Problem

Example 6-1a Find the circumference of a circle whose diameter is 6.8 centimeters. Round to the nearest tenth. Write the formula C = C = /2 Define the variable Find the circumference Bring down the C = Replace  with 3.14 C = 3.14 Replace d with 6.8 D is the diameter C = 3.14(6.8) Multiply 3.14  6.8 Round to the nearest tenth C = 21.4 Add dimensional analysis C = 21.4 cm Answer: Circumference = 21.4 centimeters

Example 6-1b Find the circumference of a circle whose diameter is 12.4 inches. Round to the nearest tenth. Answer: 38.9 in. 1/2

Example 6-2a 2/2 Monster Trucks A fleet of monster trucks uses tires mounted on 12.5-inch radius wheels. What is the circumference of a monster truck wheel? Round to the nearest tenth Write the formula What is the circumference Bring down the C = C = Replace  with 3.14 C = 3.14 Remember: The formula asks for diameter but you are given radius Multiply the radius by 2 to find the diameter C = 3.14(2  12.5)

Example 6-2a 2/2 Monster Trucks A fleet of monster trucks uses tires mounted on 12.5-inch radius wheels. What is the circumference of a monster truck wheel? Round to the nearest tenth Follow order of operations What is the circumference C =C = 3.14 C = 3.14(2  12.5) PEMDAS Work inside the parenthesis first C = 3.14( Multiply 2  12.5 Bring down C = 3.14( C = 3.14(25) Multiply 3.14  25 C = 78.5

Example 6-2a 2/2 Monster Trucks A fleet of monster trucks uses tires mounted on 12.5-inch radius wheels. What is the circumference of a monster truck wheel? Round to the nearest tenth Round to the nearest tenth What is the circumference C =C = 3.14 C = 3.14(2  12.5) C = 3.14(C = 3.14(25) C = 78.5 Answer already is to the nearest tenth Add dimensional analysis C = 78.5 inches Answer: Circumference = 78.5 inches

Example 6-2b SWIMMING POOL A new swimming pool is being built for young children at the community recreation center. The pool is circular and the distance from the center fountain to the edges is 8.5 feet. What is the circumference of the pool? Answer: C = 53.4 feet * 2/2

End of Lesson 6 Assignment Lesson 4:6 Geometry: Circumference All