Question 739871
What if the area were extended to the whole circle, {{{pi*r^2}}}, and the arc were extended to the whole circumference, {{{2*pi*r}}}?  The comparison of area to arc is {{{(pi*r^2)/(2*pi*r)=r/2}}}.  That should be the same for the area of a sector and its arc.


Using that ratio, we can make a proportion,
{{{r/2=108/12}}}, and we can easily find {{{highlight(r=2*108/12)}}}, simplify.....!