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