Whats the circumference of a circle with a diameter of 12ft

Let me tell you a secret!
You know how the formula for Circumference is 

C = 2πr

Where r is the radius? 

The reason why this formula works the way it does is because of what π IS. 

π is the ratio of ANY circle's Circumference to it's Diameter.

So you can think of π like this: 

Circumference / Diameter.
2r is the same as the diameter. So what you are doing is canceling out the diameter. Similar to what you do in algebra I to solve for x. Then you are just left with the circumference. That's pretty neat!

So, let's get to it!

2πr

Sadly, you'll most likely need to use a calculator for this problem, but if you are not permitted one then replace π with 3.14. 

What is r?
r = diameter / 2

r = 12 / 2
r = 6

2π6

If you are allowed to use a calculator then plug it in to it. If not then start doing some long multiplication!

37.699ft