Area vs circumference of a circle
Area is πr²; circumference is 2πr.
The common mistake
Mixing the formulas, or plugging in the diameter where the radius goes.
Instead: Halve the diameter to get r first. Area (space inside) uses r²; circumference (distance around) uses 2r.
Worked example with Guide me
A circle has diameter 10. Find its area.
- Sugar · What's the radius?Student · 5.
- Sugar · Square it and multiply by π.Student · 25π.
Answer: 25π ≈ 78.5
Try 3 practice questions
1. Area with radius 3?
Show answer
9π ≈ 28.3
2. Circumference with radius 4?
Show answer
8π ≈ 25.1
3. Area with diameter 14?
Show answer
49π ≈ 153.9
Quick answers
- What is the most common mistake with area vs circumference of a circle?
- Mixing the formulas, or plugging in the diameter where the radius goes.
- How do I get area vs circumference of a circle right?
- Halve the diameter to get r first. Area (space inside) uses r²; circumference (distance around) uses 2r.
- Can you show a worked example?
- A circle has diameter 10. Find its area. 25π ≈ 78.5
Related concepts
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