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⭕ Parts of a Circle

Name the centre, radius, diameter and circumference, and use diameter = 2 × radius.

2
lessons
~15 min
to learn
🔢 Math
subject
Ages 6–12
level
Start the course →

What you’ll learn

  1. The Circle's PartsName the centre, radius, diameter and circumference of a circle.A circle is a round shape with a centre in the middle. The radius is a straight line from the centre to the edge, and every radius is equal. The diameter crosses edge to edge through the centre, and the circumference is the distance all the way around.
  2. Radius, Diameter and AroundUse the rule diameter = 2 × radius (and radius = diameter ÷ 2), and describe the circumference.The diameter is always twice the radius, because it is two radius lines joined through the centre, so diameter = 2 × radius and radius = diameter ÷ 2. The circumference is the distance all the way around the outside — a circle's version of perimeter.

Questions this course answers

A straight line from the centre of a circle to its edge is the...

The radius runs from the centre to the edge.

The line that goes edge to edge through the centre is the...

The diameter crosses through the centre from edge to edge.

The middle point of a circle is called the...

The centre is the single point in the very middle.

A circle has a radius of 7 cm. What is its diameter?

Diameter = 2 × radius, so 2 × 7 = 14 cm.

A plate's diameter is 30 cm. Its radius is...

Radius = half the diameter, so 30 ÷ 2 = 15 cm.

The distance all the way around a circle is called the...

The circumference is the distance around the outside — a circle's perimeter.

Grounded in trusted sources

  • Khan Academy Kids
  • BBC Bitesize KS2 Maths
  • NRICH Maths (Cambridge)
  • Britannica Kids
  • National Council of Teachers of Mathematics

Every Wunder lesson is built from real, reputable sources — never invented.

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