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Circumferences and Areas of Circles

Use the formula for area of a circle. A = r 2. = ( 12 ) 2. Substitute. 12. Use a calculator. 452.38934. COURSE 3 LESSON 8-8. Circumferences and Areas of Circles. The diameter of a small pizza is 24 cm. Find its area. Round to the nearest tenth.

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Circumferences and Areas of Circles

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  1. Use the formula for area of a circle. A = r2 = (12)2 Substitute. 12 Use a calculator. 452.38934 COURSE 3 LESSON 8-8 Circumferences and Areas of Circles The diameter of a small pizza is 24 cm. Find its area. Round to the nearest tenth. The radius of the pizza is 24 ÷ 2, or 12 cm. Use the radius to find the area. The area of a small pizza is about 452.4 cm2. 8-8

  2. COURSE 3 LESSON 8-8 Circumferences and Areas of Circles Find the area of the unshaded region of the square tile with a circle inside of it, as shown below. Round to the nearest tenth. You can separate the figure into a circle and a square. Step 1 Find the area of the square. 8-8

  3. Substitute 12 for s. A = (12)2 = 144 Simplify. Area of circle = r2 A = (6)2 Substitute 6 for r. Multiply. Round to the nearest tenth. 113.1 COURSE 3 LESSON 8-8 Circumferences and Areas of Circles (continued) Area of square = s2 Step 2 Find the area of the circle. 8-8

  4. COURSE 3 LESSON 8-8 Circumferences and Areas of Circles (continued) Step 3 Subtract the area of the circle from the area of the square. The area of the shaded region is about 144 cm2 – 113.1 cm2 = 30.9 cm2. 8-8

  5. COURSE 3 LESSON 8-8 Circumferences and Areas of Circles Round to the nearest tenth. 1. Find the circumference and area of the circle. 2. Find the area. 18.8 km; 28.3 km2 273.0 in.2 8-8

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