Circumference Area of Circles Unit 5 3 Circumference

Circumference & Area of Circles Unit 5 -3

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

Circumference 6 cm Always write out the formula to start with Check if you have radius or diameter C = 2πr r=6 Substitute into the formula C = 2π(6) Don’t forget units! C = 12π cm or C = 37. 70 cm

Circumference C = 2πr 7. 6 cm d = 7. 6 r = 3. 8 C = 2π(3. 8) C = 7. 6π cm or C = 23. 88 cm

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

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

YOUR TURN l Given the Circumference, find the radius and diameter.

Area l Formula for Area: ** r is the radius **

Area 6 cm Always write out the formula to start with A = πr 2 Check if you have radius or diameter r=6 Substitute into the formula A = π(6)2 Don’t forget units! A = 36π cm 2 or A =113. 10 cm 2

Area A = πr 2 7. 6 cm d = 7. 6 r = 3. 8 A = π(3. 8)2 A = 14. 44π cm 2 or A = 45. 36 cm 2

YOUR TURN -Calculate the area of these circles. 4 cm 8. 2 in 50. 27 cm 2 52. 81 in 2 11 cm 95. 03 cm 2 7 ft 153. 94 ft 2

Area l Given the Area, find the radius and diameter. A = 75 ft 2

YOUR TURN l Given the Area, find the radius and diameter.