Circles: radius, diameter, circumference and Pi | Geometry | Khan Academy

What is a circle defined as?

• A shape with four equal sides

• All points that are equidistant from a central point

• A shape with no straight lines

• A closed curve that is not round

What is the term for the distance from the center of a circle to any point on its edge?

• Diameter

• Circumference

• Radius

• Arc

How is the diameter of a circle related to its radius?

• The diameter is half the radius

• The diameter is equal to the radius

• The diameter is twice the radius

• The diameter is three times the radius

What does Pi (π) represent in relation to a circle?

• The ratio of a circle's radius to its diameter.

• The ratio of a circle's circumference to its diameter.

• The ratio of a circle's area to its radius.

• The ratio of a circle's diameter to its circumference.

How is the diameter of a circle related to its radius?

• The diameter is half the radius.

• The diameter is equal to the radius.

• The diameter is twice the radius.

• The diameter is three times the radius.

A circle has a radius of 3 meters. What is its circumference?

• 3π meters

• 6π meters

• 9π meters

• 12π meters

If a circle has a circumference of 10 meters, what is its diameter?

• 10π meters

• 5π meters

• 10/π meters

• 5/π meters