Answer: ok so if the radius of the circle is one all you need to doto find the diameter is multiply it by 2 becuase the diameter is twice the radius and the radius is half the diameter for instance..if you had a diameter of four the radiace would be two becuase half of four is two.
So the formula to find the cicumfrance of a circle is C=2pir
its basically just taking the radiace which in your case is one and multaplying it by two..ok so your like now i have two what do i do..? Well thats it the answer is 2pi you would have to add the pi symbol
<--- now if it has a number in replace of the pi say 3.14, alright your like i have two and i have 3.14 what do i do...you would just have to multiply the 2 by 3.14 to get an answer of....6.28!
Explanation: I hope this helps...:D