A circle whose radius is 1/2......would have a circumference of exactly pi......easy to see from the equation for circumference.......two halves make a whole.........2 * 1/2 is 1....................1 times pi is pi......

Circle

Solve for 

circumference

C

=

2

π

r

r Radius

Circumference of a Circle - Math Goodies

www.mathgoodies.com/lessons/vol2/circumference.html

The number is the ratio of the circumference of a circle to its diameter. The value of is approximately 3.14159265358979323846...The diameter of a circle is twice the radius. Given the diameter or radius of a circle, we can find the circumference.