Question 4809
{{{C = 2 * pi * r }}}, so if you know the circumference C = 28 in, then the unknown is r.  Divide both sides by {{{2 pi}}}:

{{{20 = 2* pi *r}}}

{{{20/(2 *pi) = (2 *pi *r)/(2 *pi)}}}
{{{10/ pi = r }}}

r = 3.18 in. (approximately)


R^ at SCC