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5-Minute Check 1

A B C D. Find the circumference of the circle to the nearest tenth. Find the circumference of the circle to the nearest tenth. 5-Minute Check 1. Splash Screen. You have already found the circumference of a circle. (Lesson 11–7). Find areas of circles. Find areas of sectors. Then/Now.

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5-Minute Check 1

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  1. A B C D Find the circumference of the circle to the nearest tenth. Find the circumference of the circle to the nearest tenth. 5-Minute Check 1

  2. Splash Screen

  3. You have already found the circumference of a circle. (Lesson 11–7) • Find areas of circles. • Find areas of sectors. Then/Now

  4. sector A pie-shaped part of a circle bound by the radius of a circle and an arc • central angle An angle whose vertex is the center of the circle and whose sides are radii Vocabulary

  5. Concept A

  6. Find Areas of Circles A. Find the area of the circle. Round to the nearest tenth. EstimateA≈ 3 ● 172 or 867 A= r2 Area of a circle =  ● 172 Replace r with 17. =  ● 289 Evaluate 172.  907.9 ft2 Use a calculator. Answer: The area is about 907.9 square feet. Check907.9 ≈ 867 Example 1 A

  7. Find Areas of Circles B. Find the area of the circle. Round to the nearest tenth. EstimateA≈ 3 ● 42 or 48 A= r2 Area of a circle =  ● 4.152 Replace r with 4.15. =  ● 17.2225 Evaluate (4.15)2.  54.1 cm2 Use a calculator. Answer: The area is about 54.1 square centimeters. Check54.1 ≈ 48 Example 1 B

  8. A B C D A. Find the area of the circle. Round to the nearest tenth. A. 38.5 m2 B. 44.0 m2 C. 153.9 m2 D. 615.8 m2 Example 1 CYP A

  9. A B C D B. Find the area of the circle. Round to the nearest tenth. A. 16.3 in2 B. 32.7 in2 C. 84.9 in2 D. 339.8 in2 Example 1 CYP B

  10. Use Area of Circles to Solve Problems PICTURE FRAMES The rectangular matting for a picture frame has a circular cutout for the photograph, as shown in the figure. What is the area of the mat? Round to the nearest tenth. Example 2

  11. Use Area of Circles to Solve Problems Find the area of the rectangle minus the area of the circle. Area of rectangle Area of circle A= ℓw – r2 = 18 ● 12 –  ● 42 Replace ℓ with 18, w with 12, and r with 4. = 216 – 16 Simplify.  165.7 Use a calculator. Answer: The area is about 165.7 sq. in. Example 2

  12. A B C D The rectangular matting for a picture frame has a circular cutout as shown in the figure. What is the approximate area of the matting? A. 150.6 in2 B. 131.7 in2 C. 124.6 in2 D. 79 in2 Example 2 CYP

  13. This is tells you how big of a pie slice you are “cutting” Concept B

  14. Find the Area of a Sector Find the area of the shaded sector in the circle. Round to the nearest tenth. Area of a sector Replace N with 120 and r with 6. Simplify. Use a calculator. Answer: The area is about 37.7 m2. Example 3

  15. A B C D To the nearest tenth, what is the area of the shaded sector in the circle? A. 4.2 in2 B. 16.8 in2 C. 33.5 in2 D. 66.0 in2 Example 3 CYP

  16. End of the Lesson

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