Circumference of circle radius 3

Step by step

The question

Question: find the circumference of a circle with radius 3.

1 Use the rule

π is a special number for circles.

It is about 3.14.

The circumference is the way around the circle.

It is 2 times π times the radius: C = 2 × π × r.

So we write C = 2 × π × r.

Now put the numbers in: r = 3.

2 times 3 is 6.

We write it as 6π.

We keep π in the answer.

That is the exact answer.

2 About how much

To see about how much, put 3.14 for π.

6 times 3.14 is 18.84.

So the circumference is about 18.84.

Let's look back.

First: use the rule.

Last: about how much.