Circumference formula is [tex]2 \pi r[/tex], where r is the radius. if we set that equal to 125.6 we get [tex]2 \pi r=125.6[/tex] We can divide both sides by [tex] \pi [/tex] to get [tex]\frac{125.6}{ \pi } [/tex]. If you're confused, 2r is = to the diameter