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5-Minute Check 1

A B C D. Find the area. Find the area. 5-Minute Check 1. Splash Screen. You have already found the perimeter of rectangles. (Previous Course). Find the circumference of circles. Solve problems involving circumference. Then/Now. circle.

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5-Minute Check 1

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  1. A B C D Find the area. Find the area. 5-Minute Check 1

  2. Splash Screen

  3. You have already found the perimeter of rectangles. (Previous Course) • Find the circumference of circles. • Solve problems involving circumference. Then/Now

  4. circle The set of all points in a plane that are the same distance from a given point called the center The given point from which all points on the circle are the same distance • center • radius • chord • diameter • circumference • (pi) The distance from the center to any point on the circle A line segment whose endpoints are on a circle. A chord across through a circle’s center. Two radii are a diameter The distance around a circle The ratio of the circumference of a circle to the diameter of a circle. We typically say Vocabulary

  5. Concept

  6. Find the Circumference of a Circle Find the circumference of the circle. Round to the nearest tenth. C = 2r Circumference of a circle = 2 ●  ● 7.1 Replace r with 7.1.  44.6 Simplify. Use a calculator. Answer: The circumference is about 44.6 meters. Example 2

  7. A B C D Find the circumference of the circle to the nearest tenth. A. 5.0 cm B. 8.0 cm C. 10.1 cm D. 32.2 cm Example 2

  8. × 2nd ENTER 12 [] 37.69911184 Find the Circumference of a Circle Find the circumference of the circle. Round to the nearest tenth. C = 2rCircumference of a circle = 2 ●  ● 6 Replace r with 6 (Why?). = 12 Simplify. This is the exact circumference. To estimate the circumference, use a calculator. Answer: The circumference is about 37.7 inches. Example 1

  9. A B C D Find the circumference of the circle to the nearest tenth. A. 12 ft B. 12.6 ft C. 25.1 ft D. 50.3 ft Example 1

  10. Solve Problems LANDSCAPINGA landscaper has a tree whose roots form a ball-shaped bulb with a circumference of 110 inches. What is the minimum diameter of the hole that the landscaper will have to dig in order to plant the tree? Round to the nearest inch. Understand You know the circumference of the roots of the tree. You need to know the diameter of the hole to be dug. Plan Use the formula for the circumference of a circle to find the diameter. Example 3

  11. Solve Problems SolveC = 2r Circumference of a circle 110 = 2 ●  ● rReplace C with 110. Divide each side by . Simplify 35.0 d 2r is the diameter. Answer: The diameter of the hole should be at least 35 inches. Example 3

  12. Solve Problems Check Is the solution reasonable? Check by replacing d with 35 in C = d. C = d Circumference of a circle C =  ● 35 Replace d with 35. C  110.0 Simplify. Use a calculator. The solution is reasonable. Example 3

  13. A B C D SWIMMING POOL A circular swimming pool has a circumference of 48 feet. Matt must swim across the diameter of the pool. How far will Matt swim? A. 7.6 ft B. 15.3 ft C. 47.1 ft D. 150.7 ft Example 3

  14. End of the Lesson

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