Show:
Circumference of Circles
Radius -> Diameter
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