All About Circles

Here are some useful circle facts from KidsMathGamesOnline.com!

• A straight line from the center of a circle to the edge is called the radius.
• A straight line that passes from one side of a circle to the other through the center is called the diameter.
• The distance around the outside of a circle is called the circumference.
• All points on the edge of a circle are the same distance to the center.

• The value of Pi (π ) to 2 decimal places is 3.14, it comes in handy when working out the circumference and area of a circle.
• The circumference of a circle can be found with the following formula: Circumference = π d
• The area of a circle can be found with the following formula: Area = π r²

• An arc is part of the circumference of a circle.
• A chord is a straight line joining two points on a circle, the diameter is an example of a chord (the longest possible one).
• A segment is the region between a chord and the arc it joins.
• A tangent is a straight line that touches a single point of a circle.
• A sector is the region between an arc and two radii.

• The full arc of a circle measures 360 degrees.
• A semicircle is a shape that forms half a circle, the arc of a semicircle measures 180 degrees.
• Circles have a high level of symmetry.
• A circle has the shortest perimeter of all shapes with the same area.