Insert Lesson Title Here Circumference Vocabulary The distance

Insert Lesson Title Here Circumference Vocabulary The distance around a circle is called circumference. Course 2

Circumference CIRCUMFERENCE OF A CIRCLE The circumference C of a circle is times the diameter d, or 2 times the radius r. Formula Radius C = d, or C = 2 r Diameter Circumference Course 2

Circumference Example 1 Find the circumference of the circle to the nearest tenth. Use 3. 14 for . 12 in. C = d You know the diameter. C 3. 14 · 12 Substitute for and d. C 37. 68 Multiply. The circumference of the circle is about 37. 7 in. Course 2

Circumference Example 2 Find the circumference of the circle to the nearest tenth. Use 3. 14 for . 18 cm C = 2 r You know the radius. C 2 · 3. 14 · 18 Substitute for and r. C 113. 04 Multiply. The circumference of the circle is about 113. 0 cm. Course 2

Circumference Example 3 Find the circumference of the circle to the nearest tenth. Use 3. 14 for . 7 in. C = d C 3. 14 · 7 You know the diameter. C 21. 98 Multiply. Substitute for and d. The circumference of the circle is about 22. 0 in. Course 2

Circumference Example 4 Find the circumference of the circle to the nearest tenth. Use 3. 14 for . 11 cm C = 2 r You know the radius. C 2 · 3. 14 · 11 Substitute for and r. C 69. 08 Multiply. The circumference of the circle is about 69. 1 cm. Course 2

Circumference Helpful Hint If the diameter or radius of a circle is a 22 multiple of 7, use for p. 7 Course 2

Circumference Example 5: Application The diameter of a circular pond is 42 m. What is its circumference? Use 22 for . 7 C = d You know the diameter. C 22 · 42 7 1 22 · 42 6 C 7 1 1 C 132 Substitute 22 for and 42 for d. 7 Write 42 as a fraction. Simplify. Multiply. The circumference of the pond is about 132 m. Course 2

Circumference Example 6 The diameter of a circular spa is 14 m. What is its circumference? Use 22 for . 7 C = d You know the diameter. C 22 · 14 7 1 22 · 14 2 C 7 1 1 C 44 Substitute 22 for and 14 for d. 7 Write 14 as a fraction. Simplify. Multiply. The circumference of the spa is about 44 m. Course 2

Circumference Insert Lesson Title Here 1. If a guardrail is to be placed around the edge of a circular swimming pool with a diameter of 14 ft, how many feet of railing will be needed? Use 22 for . 7 44 ft Course 2

Circumference Insert Lesson Title Here 1/20/17 A Ferris wheel has a circumference of 440 feet. What is the approximate diameter of the Ferris wheel? 140 ft Course 2