This KS2 maths article explains how to measure the radius, circumference and diameter of a circle.

How to make handmade jewelry from copper wire by Lan Anh Handmade You can use as pendants, earrings, or used for decoration.

…and you can see that the ribbon is just over 3 times the diameter of 1 circle. This number, called π (or pi), is approximately 3.14. You have shown that the circumference of a circle is π × ...