## The Lesson

The diameter 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 diameter from the circumference: ## How to Find the Diameter from the Area

Finding the diameter from the area is easy.

## Question

What is the diameter of the circle, with area 50 cm2, below? # 1

Diameter = 2√ (Aπ)
Don't forget: √ means square root, / means ÷ and π is pi (≈ 3.14)

# 2

Substitute the area into the formula. In our example, A = 50.

Diameter = √ (50π)

Diameter = √ (50 ÷ π)

Diameter = √ (50 ÷ 3.14)

Diameter = √ 16 cm

Diameter = 4 cm

The diameter of the circle is 4 cm.

## Lesson Slides

The slider below shows another real example of how to find the diameter of a circle from the area.

## Interactive Widget

Here is an interactive widget to help you learn about finding the diameter of a circle from its area.

## Equivalent Formula for Finding the Diameter of a Circle from the Area

An equivalent formula for how to find the diameter of a circle from the area is: This is equivalent as the square root of 4 is 2.