Circumference Area of a Circle Definitions l Circumference

Circumference & Area of a Circle

Definitions l Circumference: The distance around a circle. l Diameter (d): a line that passes through the center of a circle that has its endpoints on the circle. Radius (r): half the diameter l l l d = 20, then r = 10 r = 15, then d = 30

Circumference l To find the circumference multiply the diameter, where equals 3. 14 C= times d Diameter

Circumference l Example: Find the circumference Circumference = d C = 3. 14(8) Diameter = 8 in C = 25. 12 The circumference is 25. 12 in

Circumference Example: Find the circumference Circumference = d Diameter = 2 (10) = 20 radius = 10 cm C = 3. 14(20) C = 62. 8 The circumference is 62. 8 cm

Your Turn…. Find the circumference pg. 426 # 7 -9 l No naked numbers. 7. C = d C = 3. 14(12) C = 37. 7 m l 9. C = d C = 3. 14 (16) C = 50. 2 in 8. C = d C = 3. 14(3) C = 9. 4 ft

Area of Circles l The area of a circle is the product of square of the circle’s radius r. A = r² radius and the

Area of Circles l Example: Find the area of the circle r=3 m A = r² A = 3. 14(3)² A = 3. 14(9) A = 28. 26 m² The area of the circle is 28. 26 m²

Area of Circles d = 8 in A= r² Radius = 4 in A = 3. 14(4)² A = 3. 14(16) A = 50. 24 in² The area of the circle is 50. 24 in²

Lets Review l Perimeter = Sum of all sides l Circumference = l Area of a Rectangle = ω l Area of a Triangle = l Area of a Circle = d bh r²