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Circumference & Area of Circles

Circumference & Area of Circles. Unit 5-3. Circumference. Formula for Circumference:. ** r is the radius **. ** 2 r = d. d is the diameter. **. **Circumference is the perimeter of the circle. **. Circumference. Always write out the formula to start with. C = 2 π r. 6 cm.

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Circumference & Area of Circles

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  1. Circumference & Area of Circles Unit 5-3

  2. Circumference • Formula for Circumference: ** r is the radius ** ** 2r = d. d is the diameter. ** **Circumference is the perimeter of the circle. **

  3. Circumference Always write out the formula to start with C = 2πr 6 cm Check if you have radius or diameter r = 6 Substitute into the formula C = 2π(6) C = 12π cm Don’t forget units! or C = 37.70 cm

  4. Circumference C = 2πr d = 7.6 7.6 cm r = 3.8 C = 2π(3.8) C = 7.6π cm or C = 23.88 cm

  5. YOUR TURN -Calculate the perimeter of these circles. 4 cm 8.2 in 25.13 cm 25.76 in 11 cm 34.56 cm 7 ft 43.98 ft

  6. Circumference • Given the Circumference, find the radius and diameter. C = 25 ft

  7. YOUR TURN • Given the Circumference, find the radius and diameter.

  8. Area • Formula for Area: ** r is the radius **

  9. Area Always write out the formula to start with A = πr2 6 cm Check if you have radius or diameter r = 6 Substitute into the formula A = π(6)2 A = 36π cm2 Don’t forget units! or A =113.10 cm2

  10. Area A = πr2 d = 7.6 7.6 cm r = 3.8 A = π(3.8)2 A = 14.44π cm2 or A = 45.36 cm2

  11. YOUR TURN -Calculate the area of these circles. 4 cm 8.2 in 50.27 cm2 52.81 in2 11 cm 95.03 cm2 7 ft 153.94 ft2

  12. Area • Given the Area, find the radius and diameter. A = 75 ft2

  13. YOUR TURN • Given the Area, find the radius and diameter.

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