Circumference facts for kids
Circumference is the total distance around the edge of a circle or any other closed curved shape. Think of it like walking all the way around a circular track. For shapes with straight sides, we call this distance the perimeter. But for circles, it has its own special name: circumference!
What is Circumference?
Imagine you have a hula hoop. If you measure the distance all the way around the outside edge of that hula hoop, you've found its circumference. It's how long the "line" is that makes up the circle. This measurement is super useful in many areas, from building wheels to designing round objects.
How to Measure Circumference
To find the circumference of a circle, we use a special number called pi (pronounced "pie"). Pi is a mathematical constant, which means it's always the same number, no matter how big or small the circle is. We usually use the symbol π for pi. It's approximately 3.14159.
There are two main ways to calculate circumference, depending on what you know about the circle:
- Using the diameter: The diameter is the distance straight across the circle, passing through its center. The formula is:
* Circumference = π × diameter * Or, in symbols: C = πd
- Using the radius: The radius is the distance from the center of the circle to any point on its edge. The radius is always half of the diameter. The formula is:
* Circumference = 2 × π × radius * Or, in symbols: C = 2πr
Let's say you have a bicycle wheel. If you know its diameter, you can multiply that by pi to find out how far the wheel travels in one full rotation. This is its circumference!
Images for kids
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When a circle's diameter is 1, its circumference is π.
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When a circle's radius is 1—called a unit circle—its circumference is 2π.
See also
In Spanish: Circunferencia para niños
