Question 197929
{{{C =2 * (22/7) * r}}}  Note that 22/7 is often used an approximation for pi. So this equation looks a lot like the equation for the Circumference of circle as a function of the radius.

You are asked to find C, when r = 7cm and r = 91cm

{{{C =2 * (22/7) * r}}}  Do 7 first
{{{C =2 * (22/7) * 7}}}
{{{C =2 * 22}}}
{{{C = 44}}} cm

{{{C =2 * (22/7) * r}}}  Now do r=91
{{{C = 2* (22/7) * 91}}}
{{{C = 2 * 22 * 13}}}
{{{C = 571}}} cm