Simple instructions are provided here for finding the diameter of a circle and its circumference using the standard formula and with an explanation of using Pi to find the circumference.
A circle is the set of points in a plane that are equidistant from a center point. What this basically means is that if you measured from the center point to the edge of the circle, then you should get the same measurement no matter what direction you measure from the center point. [Figure 1]
The radius of a circle [Figure 2] is the distance from the center point to any point on the circle's perimeter (edge of the circle). You use the term radii to describe more than one radius. If you decided to draw two radii at opposite sides, then you would have made a line span across the entire circle like Figure 3 below illustrates.
The diameter of a circle is two times the radius and is the span of two radii across the center point forming a straight line across the entire circle like [Figure 3]. The formula is expressed as: d=2r , where d is the diameter and r is the radius.
For example, if r=3 , then you multiply 3 by 2. In this case the diameter would be 6. d=6
You always multiply the radius x 2 to get the diameter of a circle.
Similarly, you can divide the diameter by 2 to get the radius of a circle if the radius is not known.What is the Circumference of a Circle?