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Example 9-2b Objective Find the circumference of circles

Example 9-2b Vocabulary Circle The set of all points in a plane that are the same distance from a given point called the center

Example 9-2b Vocabulary Center The given point from which all points on a circle or sphere are the same distance

Example 9-2b Vocabulary Diameter The distance across a circle through its center

Example 9-2b Vocabulary Radius The distance from the center to any point on a circle

Example 9-2b Vocabulary Circumference The distance around a circle (perimeter) C =  d or C =2  r

Lesson 9 Contents Example 1Find Circumference Example 2Find Circumference

Example 9-1a PETS Find the circumference around the hamster’s running wheel shown below. Round to the nearest hundredth. Determine if the radius or diameter has been given C = 2  3.14  3 1/2 Write formula for circumference when radius is given Bring down C = 2  Replace  with 3.14 Replace r with 3

Example 9-1a PETS Find the circumference around the hamster’s running wheel shown below. Round to the nearest hundredth. Multiply the factors C = 2  3.14  3 1/2 C = Note: If you use the  key on the calculator you will get a slightly different answer, but just remember to round to the nearest hundredth Add dimensional analysis C = inches Answer: C = inches

Example 9-1b SWIMMING POOL A new children’s swimming pool is being built at the local recreation center. The pool is circular in shape with a diameter of 18 feet. Find the circumference of the pool. Round to the nearest hundredth. Answer: ft 1/2

Example 9-2a Find the circumference of a circle with a diameter of 49 centimeters. Answer: C = cm Write the formula for circumference of a circle using diameter Bring down C = C = 3.14(49) C = /2 Replace  with 3.14 Replace d with 49 Multiply Add dimensional analysis C = cm

Example 9-2b Find the circumference of a circle with a radius of 35 feet. Answer: C = ft * 2/2

End of Lesson 9 Assignment Lesson 6:9Geometry: Circles and All Circumference