# Basic Geometry : How to find the length of a radius

## Example Questions

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### Example Question #31 : How To Find The Length Of A Radius

True or false: A circle with diameter 25 has radius 12.5.

False

True

True

Explanation:

The radius of a circle is one half (or 0.5) times its diameter, so a circle with diameter 25 has radius .

### Example Question #31 : How To Find The Length Of A Radius

Use 3.14 for pi in the following question.

If the area of a circle measures , what is the length of its radius?

Explanation:

First we need to know the formula for area of a circle  where r is the radius and pi is 3.14. We plug in what we know so we get an equation that looks like this

We need to solve for r so first we divide both sides by pi (3.14)

Then we take the square root of both sides.

Since the square root of 400 is 20, the measure of the radius is 20cm

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