- The circumference of a circle is also known as the perimeter of a circle
- We calculate the circumference of a circle by using the formula
- circumference = π × diameter = π × 2 × radius = π × 2r = 2 π r
- To find area of circle, we use; area = π × radius × radius = π r²
E.g Find the circumference and area of circle A and B below. ( Take π = 3.14 )
Circumference = π × diameter = 3.14 × 20 = 62.8 cm
Radius = 20 ÷ 2 = 10 cm
Area = π r² = 3.14 x10 x10 = 314cm²
Circumference = 2 π r = 2 x 3.14 x 5 = 31.4 cm
Area = π r ² = 3.14 x 5 x 5 = 78.5 cm²