Finding Circumference for 4 th and 5 th Grade By Andrea Klee

What Is Circumference Circumference is the distance all the way around a circle. The equation to find circumference is 2  r or  multiplied by the diameter of the circle.

Some Terms Defined  is said as pie, like the kind you eat – about 3.14 r is the radius of a circle – or half the distance across a circle d is the diameter of a circle – or the distance all the way across a circle – or two radii added together

How To Find Circumference If you have the radius: – Multiply the radius by 2 to get the diameter. – Multiply this answer by 3.14 (  ). If you have the diameter: – Multiply the diameter by 3.14 (  ).

Let’s Try A Problem Find the diameter or the radius. We are going to find the radius. What is the radius of this circle?

Problem Continued The radius is 5. Next, multiply the radius by 2 to get the diameter. Last, multiply the diameter by  or 3.14.

Problem Solved The circumference of the circle is 31.4.

Here’s Another Problem Find the circumference of this circle.

Solution The diameter is 6. Multiply the diameter by  (3.14). The Circumference is

Links Math.com has everything you might want to know about the parts of circles. This site defines circle, pie, circumference, diameter, and radius. –

Links Prime Mathematics Enrichment is a magazine that has fun projects to do involving circles. –

Links Math Forum’s Ask Dr. Math This page is a letter sent to Dr. Math asking how the circumference of the Earth was first measured. This offers a little history about circumference. –