Math 7, Circles

Circumference

The distance around the circle.

What is the circumference of a circle when the diameter is 12 meters? In term of π.

C = 12π meters

What is the circumference of a circle when the radius is 9 inches? In terms of π.

C = 18π inches

What is the circumference of a circle when the radius is 5 feet? Use 3.14 for π.

C = 31.4 feet

What is the circumference of a circle when the diameter is 12 centimeters? Use 3.14 for π.

C = 37.68 centimeters

C = πd or C = 2πr

Circumference Formula

Perimeter

Distance around a figure

What is the Area of the circle, when the radius is 6 centimeters? Use 3.14 for π.

A = 113.04 Square Centimeters

What is the Area of the circle, when the diameter is 22 meters? Use 3.14 for π.

A = 379.94 Square meters

What is the Area of the circle, when the diameter is 53.5 inches? In terms of π.

A = 715.56π Square Inches

The area of a circle is equal to π times the radius squared.

A =πr^( 2) or A = π*r*r

Diameter

A line segment that passes through the center of the circle and whose endpoints lie on the circle.

Radius

A line segment with one endpoint at the center of the circle and the other endpoint on the circle