Level 72 Level 74
Level 73

Circumference & Area of a Circle


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Circle (definition)
All points are the same distance from the center
Radius (definition)
The distance from the center to the edge of a circle
Diameter (definition)
Starts at one side of the circle, goes through the center and ends on the other side.
Circumference (definition)
The distance around the edge of the circle
When you divide the circumference by the diameter
You get 3.141592654... . which is the number π (Pi)
C=πd
Circumference formula with diameter
C=2πr
Circle (circumference)
A=πr²
Area formula with radius
d=14 in
A=πr² and C=2πr
C=15.7 cm
What is the circumference of a circle with diameter of 5 centimeters? A=πr² and C=2πr
A=38.47 ft²
A=πr² and C=2πr
r=4.5 cm
What is the radius of a circle with a diameter of 9 centimeters? A=πr² and C=2πr
d=9 in
If the circumference of a circle is 28.26 inches, then what is its diameter? A=πr² and C=2πr
r=2 cm
If the area of a circle is 12.56 square centimeters, then what is its radius? A=πr² and C=2πr
C=25.12 m
What is the circumference of a circle if its radius is 4 meters? A=πr² and C=2πr
A=63.58 cm²
A=πr² and C=2πr
d=7 ft
The distance around a bicycle wheel is 21.98 feet. What is its diameter? A=πr² and C=2πr
d=4 cm
The area of a DVD is 12.56 square centimeters. What is its diameter? A=πr² and C=2πr
r=2.5 in
The circumference of a dinner plate is 15.7 inches. What is its radius? A=πr² and C=2πr
What is the relationship between the diameter & circumference?
The circumference is slightly more than 3 times the diameter.
What is the relationship between the circumference & radius?
The circumference is slightly more than 2π or 6 times more than the radius