Area of a Circle
The space enclosed inside a circle of radius r.
A = \pi r^2
1What it means
Area grows with the square of the radius, so doubling the radius makes the area four times larger. Use π ≈ 22/7 or 3.14.
2Variables
| Symbol | Meaning |
|---|---|
| A | Area |
| r | Radius (centre to edge) |
| \pi | Pi ≈ 22/7 ≈ 3.14 |
3Worked examples
Example 1 Worked solution
Q. Find the area of a circle of radius 7 cm (π ≈ 22/7).
- A = π r² = (22/7) × 7².
- = (22/7) × 49.
- = 22 × 7.
✓ A = 154 cm²
4Where it's used
- ✦Finding the area of circular fields, plates, pipes and tanks.
- ✦Comparing pizza/region sizes by radius.
5Tips & common mistakes
- !Use radius, not diameter — if given the diameter, halve it first.
- !Choose π = 22/7 when the radius is a multiple of 7; otherwise 3.14.