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
