The circumference of a circle, which is another way of saying the perimeter of a circle, can be found using the formula 2πr.
Note that π represents the irrational number 3.14159... which
rounds to 3.14 and r represents the radius of the circle.
Therefore, since π = 3.14, another way of writing the formula
for the circumference of a circle is 2 · 3.14r or 6.28r.