Circles
โญ MasteredA circle has a centre, a radius from the centre to the edge, and a diameter across the middle. The diameter is twice the radius.
Pi (ฯ) is about 3.14 and is the ratio of a circle's circumference to its diameter.
All about Circles
A circle is a round shape where every point on the edge is the same distance from the centre. The distance from the centre to the edge is the radius. The distance straight across the circle through the centre is the diameter.
The diameter is always twice the radius. The distance around the outside of a circle is its circumference. Pi (about 3.14) links the circumference to the diameter: circumference = ฯ ร diameter.
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Real-life uses of Circles
- Measuring the size of a wheel or bicycle tyre
- Cutting pizzas and cakes into equal slices
- Designing round clocks, coins and plates
Frequently asked questions about Circles
What is the difference between radius and diameter?
The radius goes from the centre to the edge. The diameter goes across the whole circle through the centre and is twice as long.
What is pi?
Pi is the ratio of a circle's circumference to its diameter. It is approximately 3.14159 and never ends or repeats.
How do you find the area of a circle?
Multiply pi by the radius squared: area = ฯ ร r ร r.