Parts of a circle

Part of Maths2D shapesYear 6Year 6

What is a circle?

A circle is a shape where every point at its edge is the same distance from the centre.

A circular shape or object is one that is in the form of a circle.

How many of these circular objects can you name?

Circular objects including a frisbee, beach ball, clock, football and hula hoop.
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Quiz: Parts of a circle

Test out your knowledge of circles with this quiz, then read on to complete the page.

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Parts of a circle

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  1. A blue circle with a dot in the centre and a red dotted line drawn around the outside to show the circumference.

    Circumference

    The circumference is the distance all the way round a circle.

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Example 1

The radius is the distance halfway across the circle, from the centre to the circumference. The radius is always half the length of the diameter.

A circle with a line from it's centre to edge marking the radius of 6cm.

If you know the radius of this circle is 6cm, can you work out the diameter?

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Example 2

If you know the length of the diameter of a circle, you can halve it to work out the length of the radius.

A circle with a dot marking the centre and a line across the circle showing a diameter of 18cm.

If you know the diameter of this circle is 18cm, can you work out the radius?

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Example 3

Concentric circles are circles with the same centre point, but the length of their radius is different.

If you throw a pebble in a pond, the ripples show concentric circles.

Concentric circles in a pond. The centre circle has a radius of 2cm.

These concentric circles increase the length of the radius by 2cm each circle.

Can you work out the diameter of the largest circle?

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Use your times tables and more maths skills to defeat monsters and reclaim the Kingdom of Mathematica

Play our fun maths game Guardians: Defenders of Mathematica
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