The radius of a circle is 4 kilometers. What is the circle's circumference?

Question

anonymous · Answer

the circumference of a circle is calculated by 2r, where r is the radius. what do you think the circumference is?

anonymous · Answer

i have no idea thats why im asking you guys

anonymous · Answer

8 maybe idk

anonymous · Answer

exactly ^.^ you got it

anonymous · Answer

is that the answer

anonymous · Answer

yup

anonymous · Answer

oh pellet, sorry haha its actually 2$$\pi \pi$$

anonymous · Answer

grr that didn't do it correctly. 
the formula is $$2pir$$
so the answer is actually $$8\pi$$
sorry about that!

anonymous · Answer

The diameter of a circle is 4 kilometers. What is the circle's circumference?

anonymous · Answer

the diameter is just 2r, so if the diameter is 4, divide it by 2 to get the radius
once you have that, plug it into the circumference formula to get your answer 
$$2(2)\pi$$

or you might notice that you're doing an extra step unnecessarily, and you can just see that the forumla is also $$c=D \pi$$ where d is the diameter

anonymous · Answer

The diameter of a circle is 6 kilometers. What is the circle's circumference?
Sorry im asking a lot if u have ever heard of IXL i hae to do it up till 90 or 80

anonymous · Answer

The radius of a circle is 3 centimeters. What is the circle's circumference?
nevermind that one

anonymous · Answer

using the formula i just gave you, what do you think it is?

anonymous · Answer

so 2rPi, when r = 3?