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Lesson Menu. Main Idea and New Vocabulary Key Concept: Circumference of a Circle Example 1: Find the Circumferences of Circles Example 2: Find the Circumferences of Circles Key Concept: Area of a Circle Example 3: Find the Areas of Circles Example 4: Real-World Example.

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  1. Lesson Menu Main Idea and New Vocabulary Key Concept: Circumference of a Circle Example 1: Find the Circumferences of Circles Example 2: Find the Circumferences of Circles Key Concept: Area of a Circle Example 3: Find the Areas of Circles Example 4: Real-World Example

  2. Find the circumference and area of circles. • circle • center • radius • chord • diameter • circumference • pi Main Idea/Vocabulary

  3. Key Concept

  4. Use a calculator to find 5. 5 [] 15.70796327 2nd ENTER × Find the Circumferences of Circles Find the circumference of the circle. Round to the nearest tenth. C = dCircumference of a circle C = •5Replace d with 5. C = 5 This is the exact circumference. Answer: The circumference is about 15.7 feet. Example 1

  5. Find the circumference of the circle. Round to the nearest tenth. A. 12.6 cm B. 25.1 cm C. 50.3 cm D. 201.1 cm Example 1 CYP

  6. Find the Circumferences of Circles Find the circumference of the circle. Round to the nearest tenth. C = 2rCircumference of a circle C = 2 • •3.8Replace r with 3.8. C ≈ 23.9 Use a calculator. Answer: The circumference is about 23.9 meters. Example 2

  7. Find the circumference of the circle. Round to the nearest tenth. A. 22.6 mm B. 45.2 mm C. 162.9 mm D. 325.7 mm Example 2 CYP

  8. Key Concept 4

  9. Find the Areas of Circles Find the area of the circle. Round to the nearest tenth. A = r2Area of a circle A = (5)2Replace r with half of 10 or 5. A =  • 25 Evaluate 52. This is the exact area. A ≈ 78.5 Use a calculator. Answer: The area is about 78.5 square inches. Example 3

  10. Find the area of the circle. Round to the nearest tenth. A. 47.1 yd2 B. 94.2 yd2 C. 176.7 yd2 D. 706.9 yd2 Example 3 CYP

  11. Divide each side by . TREES The circumference of a tree is 84 inches. What is the approximate diameter of the tree? C= d Circumference of a circle 84= dReplace C with 84. 26.7 ≈ d Use a calculator. Answer: The diameter of the tree is about 27 inches. Example 4

  12. BICYCLES The circumference of a bicycle wheel is 53.4 inches. What is the approximate diameter of the wheel? A. 9 in. B. 15 in. C. 17 in. D. 20 in. Example 4 CYP

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