Vocabulary

Circle – the set of all points in a plane that are the same distance from one fixed point.

Center – one point in the middle of a circle that is the same distance from all of the points on the circle.

Diameter – the distance across a circle that passes through the center.

Radius – the distance from the center to any point on the circle.

Concepts

Finding the radius and diameter of a circle.

Rules

1. Determine whether you are given the radius or the diameter of the circle.
2. If you are given the diameter, divide it by 2 to get the radius.
3. If you are given the radius, multiply it by 2 to get the diameter.

Example

What is the radius of the circle below?

Select the correct answer.

Solution

The given dimension is the diameter. The radius is half the value of the diameter.

Answer: 3.5 m

Pre-requisite Skills

Circles: Diameter, Radius, Circumference (6.11.1)