Circumference of Circles
Radius -> Diameter
Diameter -> Radius
Diameter -> Radius
All about Circles
Area of Circles
STAAR Problems
100
What does circumference mean?
Circumference is the distance around the outside of a circle.
100
What is the radius of a circle with a diameter of 22 cm?
11 cm
100
What is the radius of a circle with a diameter of 12 cm?
6 cm
100
What does area mean?
Amount of space that a shape (circle) is taking up.
100
Emily bought a new circular dining room table with a radius of 2 feet. She wants to decorate the outer edge of the table with wooden beads. What does Emily need to calculate and what formula should she use?
Circumference, C = 2 π r
200
What is the circumference of a circle with a radius of 2 cm?
BONUS: Draw a picture of a circle with a radius for an extra 10 100 pts
6.28 cm
200
What is the radius of a circle with the diameter of 84 cm?
42 cm
200
Which is longer the radius or diameter?
Diameter
200
What is the area of a circle with a radius of 35cm?
3846.5 cm2
200
Avery is designing a platform for a local theater company. He plans to paint a red circle, the circle has a radius of 2 cm. If he wants to figure out how much paint is needed to cover the circle, what does he need to calculate and which formula can he use?
Area, A = π r2
300
What is the circumference of a circle with a diameter of 6 cm?
BONUS: Draw a picture of a circle with a diameter for 100 pts
18.84 cm
300
What is the diameter of a circle with the radius of 14 cm?
28 cm
300
What is the ratio that describes pi?
(Hint: you may write this as a fraction)
Pi is the ratio of the circumference of a circle to the diameter of a circle.
π = C / d
300
What is the equation for area of a circle?
Area= 3.14 x r2
300
What is area of a pizza with diameter of 20 ft? 
A = π r2 ; (d=20 ft so r=10 ft)
A = 3.14 x 102
A = 3.14 x 100
A = 314 ft2
400
Which circle has the greatest length of circumference?
Circle A: Radius = 4 cm
Circle B: Diameter = 6 cm
Circle A has a greater circumference
400
What is the diameter of a circle with a radius of 100 cm?
200 cm
400
What does pi equal?
3.14
400
What is the area of a circle that has a diameter of 22ft?
?
379.94 ft2
400
*** DOUBLE JEOPARDY ***
The circumference of a circle is 18 cm. What is the radius? (write your answer to the nearest hundredth ._ _)
C = 2 π r
18 = 2 x 3.14 x r
Divide 18 by 2 = 9
Divide 9 by 3.14
r = 2.86 cm
500
What is the circumference of a cirlce with a radius of 6 cm?
37.68 cm
500
What is the radius of a circle with a diameter of 100cm?
50 cm
500
How do you find the circumference of a circle?
Multiply 3.14 times the Diameter
C = 3.14 x D
500
What is the area of a circle with a diameter of 5 cm?
19.625 cm2
500
Logan runs laps at the local high school. It is a circular track with a diameter of 44 feet. How far does he run after completing one lap?
138.16 ft