In this Instructable, we will dive into the exciting world of Circles.
Specifically the Circumference of a Circle.

Supplies:
Pencil (needed for it's erase-ability)
Paper

## Step 1: Circle

Some basics of the Circle:

Circumference - the distance around the circle (aka the perimeter of the circle)
Radius - the distance from the center to any point on the circle
Diameter - the distance from a point on the circle to another point on the circle going
through the center (also twice the length of the Radius)
Pi - the symbol that represents the value 3.14 (actually Pi is a never ending number, but for our purposes 3.14 will be fine)

## Step 2: Circumference

Now to find the Circumference

Formulas for Circumference:
C = 2*Pi*r
C = Pi*d

d - diameter

General Steps for solving:
1) write the formula you will use
2) write the information Given
3) substitute the given information into the formula

Example 1:
Given: circle with a radius = 4 cm
1) C = 2*Pi*r (choose this formula because you are given a radius)
2) r = 4
3) C = 2*Pi*4
4) C = 8*Pi
4) C = 8*3.14
5) C = 25.12 cm (don't forget your units)

Example 2:
Given: circle with a diameter = 12 in.
1) C = Pi*d (choose this formula because you are given a diameter)
2) d = 12
3) C = Pi*12
4) C = 3.14*12
5) C = 37.68 in. (don't forget your units)
3.1415926535897932384626433832795028841961693993751058209749445923078164062862089986280348
Ive got 88! Memorized it fir a contest.<br/><br/>3.1415926535897932384626433732795028841971693993751058209749445923078164062862089986280348<br/><br/>Plz tell me if i messed up
off the top of my head, pi is equal to 3.141592653589793. i have it to a million on my comp
I only have it memorized to 3.14159.&nbsp; I like to show my students the websites that let you search for your b-day, phone number, ss#, etc in pi<br /> like this<br /> http://www.angio.net/pi/piquery<br />
in example 2 of step 2 you show that the radius is 12 in. Don't you mean the diameter?
You are correct.&nbsp; Thank you for pointing it out.&nbsp; I fixed the page. :-)<br />
I know it's not as precise, but 22/7 works for a close guesstimate.