Slope-Intercept Form
9-12
1
Circumference and Area of a Circle
Lesson Details
Grade Level
6-8
Duration (minutes)
2
Summary
A Grade 6-8 math lesson teaching students how to find the circumference and area of a circle using the formulas C = 2πr and A = πr², including how to find the radius from a given diameter, with two fully worked examples.
Student Worksheet: Circumference and Area of a Circle
Teacher Note: Students can watch the video lesson above and answer the questions. Click the “Teacher Answer Key” dropdown below when you are ready to review the solutions!
Key Concepts:
• Radius & Diameter: The radius goes from the center to the edge of the circle; the diameter goes all the way across through the center. Diameter = 2 × radius.
• Pi (π): A special number used with circles, approximately 3.14.
• Circumference: The distance around a circle. C = 2 × π × r, measured in regular units.
• Area: The space inside a circle. A = π × r × r, measured in square units.
Instructions: Read each question carefully and write your answer in the space provided. Use π ≈ 3.14.
- Question 1: What is the formula for the circumference of a circle?
- Question 2: What is the formula for the area of a circle?
- Question 3: A circle has a radius of 6. Find the circumference.
- Question 4: A circle has a diameter of 14. Find the radius, then find the area.
- Question 5: Why does area use square units while circumference uses regular units?
Click to reveal Teacher Answer Key
1. C = 2 × π × r
2. A = π × r × r
3. C = 2 × 3.14 × 6 = 37.68, so C ≈ 37.7 units.
4. Radius = 14 ÷ 2 = 7. A = 3.14 × 7 × 7 = 153.86, so A ≈ 153.9 square units.
5. Circumference measures a distance (one dimension) around the circle, while area measures the space (a two-dimensional region) inside it — so area must be measured in square units.
Disclaimer: This worksheet was generated with AI assistance based on original video content. It is intended for educational reference only. Teachers are encouraged to review and adjust questions to fit their curriculum standards before classroom use.
🎯 Extension Activity: Measure the diameter of a circular object at home (like a plate or a clock face) in inches or centimeters. Then calculate its radius, circumference, and area using π ≈ 3.14.