Area of a circle
The formula for the area of a circle is one of the most powerful and useful in mathematics. It is difficult to see how we could otherwise calculate the area of something with no straight lines - a triangle can be linked to a rectangle fairly easily, but a circle cannot. However, this formula is actually derived in a similar way.
The formula involved using the radius only. If you are given the diameter, you can half this to find the radius, because two radii make one diameter.
Problem solving using the area of a circle (including leaving the answer in terms of pi).
- BBC Bitesize: Notes and a couple of worked examples
- IXL: Online problems with solutions (also includes circumference of a circle)
- Manga High: Online activity with lots of practice problems on area of a circle