Circle Vocabulary
What are the 4 main parts of a circle?
A circular plate has a radius of 4 cm. Which formula would you use to find the distance around the plate?
C = 2πr or C = πd
A circle has a radius of 3 cm. Find its diameter.
d = 2r = 6 cm
The clock on your classroom wall has a radius of 6 inches. About how far does the second hand travel in one full circle?
C = 2πr = 2π(6) ≈ 37.68 in.
You just walked into class. What’s the first thing you should do before the lesson begins?
Sit in your assigned seat and get materials ready.
Describe what the Diameter is.
The line from one side of the circle to the other, passing through the center.
The diameter of a bicycle wheel is 20 inches. Write and solve the formula to find its circumference.
C = πd = π(20) ≈ 62.8 in.
A circle has a diameter of 8 inches. What is its circumference?
C = πd = π(8) ≈ 25.1 in.
You’re designing a round sticker with a diameter of 6 cm. How much space will it cover?
A = πr2 = π(3)2 ≈ 28.3 cm2
During the lesson, you have a question. What should you do before speaking?
Raise your hand and wait to be called on.
What special number is present in both Formulas for Area and Circumference?
Pi or 3.14
A pizza has a radius of 6 inches. Which formula helps you find how much pizza there is to eat, and what is the area?
Area formula — A = πr2 = π(6)2 ≈ 113.1 in2
A small clock has a radius of 5 cm. Find its area using the correct formula.
A = πr2 = π(5)2 ≈ 78.5 cm2
A basketball hoop has a diameter of 18 inches. What is the circumference of the rim?
C = πd = π(18) ≈ 56.5 in.
Your Chromebook is open, but we’re working on whiteboards. What should you do?
Close it — only use technology when instructed.
If a circle has a diameter of 10 cm, what is its radius? Explain how you know.
5cm.
The relationship between the diameter to radius is Radius = Diameter / 2
You measure the distance around a circular fountain and find it’s 31.4 feet. What formulas would you use to find the radius?
r = 31.4/2π
The circumference of a bike wheel is 31.4 inches. Use a formula to find the radius.
r = C/2π = 31.4/6.28 ≈ 5 in.
A pizza has a radius of 5 inches. How much crust (the edge) goes all the way around?
C = 2πr = 2π(5) ≈ 31.4 in
A classmate is speaking during discussion. What is your job?
Stay silent, listen attentively, and show respect.
Explain the difference between circumference and area in your own words.
Circumference is the distance "around" the circle.
Area is the space "inside" the circle.
A clock face has a circumference of 75.4 cm. What're the correct formulas, to find both the radius and area of the clock face.
r = 75.4/2π ; A = πr2
A circular garden has a radius of 7 feet. Find both its circumference and area.
C = 2πr = 2π(7) ≈ 43.98 ft
A = πr2 = π(7)2 ≈ 153.9 ft2
A circular garden fountain has a radius of 6 feet. How many square feet of space does it take up?
A = πr2 = π(6)2 ≈ 113.1 ft2
The class is working as a team on Jeopardy. What does “respect each other and the space you’re in” look like?
Use kind language, take turns, keep materials organized, and encourage teammates.