advertisement

Area of circles To calculate the area of a circle, we use the formula: Area = pi x (radius squared) A = π x r2 Example 1: The radius of a circle is 10 cm. A = π x r2 A = 3.14 x 102 A = 3.14 x (10 x 10) A = 3.14 x 100 Area = 314 cm2 Example 2: The diameter of a circle is 10 mm. First, we need to find the radius. The radius is 5 mm (10 ÷ 2 = 5). A = π x r2 A = 3.14 x 52 A = 3.14 x (5 x 5) A = 3.14 x 25 Area = 78.5 cm2 Remember: 82 = 8 x 8 = 64 62 = 6 x 6 = 36