# How to Find the Radius from the Circumference (Mathematics Lesson)

# What Is the Radius in Terms of the Area?

The radius of a circle is the square root of the area of a circle divided by π.# How to Find the Radius from the Area

**Question:**What is the radius of the circle, with area A, below?

**Step 1:**Divide the area, A, by π.

A ÷ π =

^{A}⁄

_{π}

**Step 2:**Take the square root.

√

^{A}⁄

_{π}

This is the radius, r, of the circle.

# A Real Example of How to Find the Radius from the Area

**Question:**What is the radius of the circle, with area 10cm

^{2}, below?

**Step 1:**Divide the area, 10cm

^{2}, by π.

10 ÷ π = 10 ÷ 3.14 = 3.18cm

^{2}

**Step 2:**Take the square root.

√ 3.18 = 1.78cm

The radius of the circle is 1.78cm.

# Another Real Example of How to Find the Radius from the Area

The slider below shows another real example of how to find the radius of a circle from the circumference:##### Curriculum

##### Interactive Test

**show**

##### Note

**WHAT IS A CIRCLE?**

A circle is a shape containing a set of points that are all the same distance from the center. This distance is the radius.