Question 947550
Original circumference, {{{2(pi)r}}}.


Increased radius, {{{r+6/2}}};


Increaese of area,  {{{pi*(r+6/2)^2-pi*r^2=45*pi}}}
{{{(r+3)^2-r^2=45}}}
{{{r^2+6r+9-r^2=45}}}
{{{6r-9=45}}}
{{{6r=45+9}}}
{{{6r=54}}}
{{{highlight(r=9)}}}, the original radius.


The original circumference was {{{2(pi)*9}}} or {{{highlight(18(pi))}}}.