Parts of a Circle
What do we call the distance from the center of a circle to its edge?
Radius
What formula finds a circle’s circumference using its diameter?
C = pi x d
What formula finds the area of a circle?
A = pi x r2
What fraction of a full circle is a semicircle?
1/2
What fraction of a full circle is a quarter circle?
1/4
What do we call a line segment that passes through the center and connects two points on the circle?
Diameter
Find the circumference of a circle with radius 4 cm. Give your answer in terms of pi.
C = 8pi cm
Find the area of a circle with radius 3 cm. Give your answer in terms of pi?
A = 9pi cm2
Find the area of a semicircle with radius 4 cm. Give your answer in terms of pi.
8pi cm2
Find the area of a quarter circle with radius 4 cm. Give your answer in terms of pi
A = 4pi cm2
A circle has a radius of 6 cm. What is its diameter?
12cm
A circular pond has a diameter of 10 m. What is its circumference in terms of pi?
C = 10pi m
A circular table has a diameter of 12 ft. What is its area in terms of pi?
A = 36pi ft2
A semicircle has a diameter of 10 m. What is its area in terms of pi?
A = 12.5pi m2
A quarter circle has a radius of 8 m. What is the area in terms of pi?
A = 16pi m2
The diameter of a circle is 18 inches. What is its radius?
9 in
A circular track has a radius of 14 m. How far is one lap, in terms of pi?
C = 28pi m
A circular garden has a radius of 7 m. What is its area in terms of pi?
A = 49pi m2
what is the formula for a semi-circle?
A = 1/2 pi r2
A quarter circle has a diameter of 12 in. What is its area in terms of pi?
A = 9pi in2
A circle’s circumference is 20pi centimeters. What are its diameter and radius?
diameter: 20 cm
radius: 10cm
A circle’s circumference is 36pi inches. What is its radius?
r = 18 in
A circle has an area of 81pi square centimeters. What is its radius?
r = 9
A semi-circle has a diameter of 30 cm, what is the area in terms of pi?
A = 112.5 pi cm2
What is the formula for a quarter circle?
A = 1/4 pi r2