Area of a circle
You learn to work out the area of a circle.
How to work it out
- Multiply radius by itself: r × r.
- Multiply that by π (approximately 3.14).
A worked example
A circle has radius 3 cm. What is the area?
- Radius times radius times π: 3 × 3 × 3.14 = 28.26.
- The area is about 28.3 cm².
Another example
A circle has radius 5 m. What is the area?
- Radius times radius times π: 5 × 5 × 3.14 = 78.5.
- The area is about 78.5 m².
Watch out
You multiply the radius by 2 instead of by itself: with radius 5 you work out 10 × 3.14.
That is the circumference. For the area you do 5 × 5.
You forget the ² in your answer.
An area is always a square unit: cm² or m².
Tips
- Area = radius × radius × π.
Why it works
The area is radius times radius times π. The radius is from the middle to the edge. If the radius is 3, the area is 3 × 3 × 3.14 = about 28.3.