The LessonThe radius of a circle is found from the area of a circle using the formula: In this formula, A is the area of the circle. The image below shows what we mean by finding the radius from the area:
How to Find the Radius from the AreaFinding the radius from the area is easy.
QuestionWhat is the radius of the circle, with area 10 cm2, below?
Start with the formula:
Radius = √ (A⁄π)Don't forget: √ means square root, / means ÷ and π is pi (≈ 3.14)
Substitute the area into the formula. In our example, A = 10.
Radius = √ (10⁄π) Radius = √ (10 ÷ π) Radius = √ (10 ÷ 3.14) Radius = √ 3.18 Radius = 1.78 cm