Converting a circle's diameter to a straight length? Assume we have a circle:

That circle's diameter is $m$, if that circle was a string, and we extended the string to a straight line, what would the length be? $m$ or $2m$?

The ratio of the length (circumference) of a circle, $C$ to its diameter $m$  is $\pi$ (a Greek letter spelled pi and pronounced "pie" in English-speaking countries).  The decimal representation of $\pi$ continues forever without repeating after the decimal point:  $\pi = 3.14159265...$
So if $C/m = \pi$, then $C = m \cdot \pi.$
