Finding Circumference

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Presentation transcript:

Finding Circumference 9.2 Finding Circumference How do you find the circumference of a circle?

ADDITIONAL EXAMPLE 1 Find the circumference of the circle to the nearest hundredth. Use 3.14 for . about 28.26 in.

ADDITIONAL EXAMPLE 2 A circular wading pool at a park has a radius of 21 feet. Find the circumference of the pool. Use for . about 132 ft

ADDITIONAL EXAMPLE 3 A circular concrete patio has a circumference of about 1,400 feet. A gardener walks directly across the patio along a radius at a rate of 1.5 feet per second. How long does it take him to get from the edge of the patio to the plant at the center? about 149 sec or about 2 min 29 sec

9.2 LESSON QUIZ 7.9.B For 1–3, find the circumference of each circle. Use 3.14 or for . Round to the nearest hundredth if necessary. 1. a circle with radius 63 mm about 396 mm 2. a circle with diameter 6.2 in. about 19.47 in. 3. a circle with diameter 18 in. about 56.52 in.

4. A circular satellite dish antenna has a circumference of about 62.8 inches. Find its diameter. 20 in. 5. The diameter of a bicycle’s tires is 2.5 feet. How many revolutions of the tires does it take to travel 1 mile? Use 5,280 feet = 1 mile. Round to the nearest tenth. 672.6 revolutions

6. a. The Jones family wants to enclose their circular garden with a fence. To the nearest foot, what is the minimum length of fencing they need to buy? 393 ft b. If the fence costs $2.50 per foot, what will be the total cost? $982.50

How do you find the circumference of a circle? Sample answer: Use C = d or C = 2 r, where C is the circumference, d is the diameter, and r is the radius. Use 3.14 for .