Radius, Diameter, Circumference and Area of Circles
Circle
A figure (shape) whose boundary consists of points all of which are equidistant (the same distance) from its center
Radius of a circle
A line that connects the center of the circle with any point on the circle.
Diameter of a circle
A line that connects two points on the circle and passes through the center.
16.0 feet
If the area of a circle is 201.06 square feet, what is its diameter to the nearest tenth of a foot?
25.12 centimeters
If the area of a circle is 50.24 square centimeters, what is the circumference of the circle?
5.0 inches
If the area of a circle is 78.5 square inches, what is its radius to the nearest tenth of an inch?
4.5 in
The circumference is 28.26 in, what is the radius?
12 in
The circumference is 37.68 in, what is the diameter?
3.14 in²
The circumference is 6.28 in, what is the area of the circle?
1 ft
The diameter of a circle is 2 ft. What is its radius?
Circumference of a circle
The distance around a circle ("perimeter" of the circle)
36 yd
The radius of a circle is 18 yards. What is its diameter?
Circumference
What does the black line in the diagram represent?
3.14
What is the approximation that we use for this mathematical symbol.
415.3 miles squared
What is the area of a circle if its radius is 11.5 miles? Round your answer to the nearest tenth. Use 3.14 for pi.
55.4 m squared
What is the area of this circle with a diameter of 8.4 meters? Round your answer to the nearest tenth. Use 3.14 for pi.
56.5 yd
What is the circumference of a circle if its diameter is 18 yards? Use 3.14 for pi and round your answer to the nearest tenth.
43.96 km
What is the circumference of a circle if its radius is 7 km? Use 3.14 for pi and round your answer to the nearest hundredth.
Radius
What is the line in the diagram below called?
Diameter
What is the line in the diagram called?
π
What number do you get when you divide the circumference of a circle by its diameter?
