Question 979530
Two radii and the length of the arc with this radius.


{{{(140/360)pi*r^2=126pi}}}
The fraction of the full-circle's area given to be equal to {{{126pi}}}.


{{{(7/18)pi*r^2=126pi}}}
{{{r^2=126pi(18/7)/pi}}}
{{{r^2=(18^2)}}}
{{{highlight(r=18)}}}


The length of the arc,  {{{2pi*r(140/360)=(2*7/18)pi*r=(2*7/18)*18*pi=highlight(14pi)}}}.


The perimeter of this sector is {{{r+r+14pi=18*2+14pi=highlight(highlight(36+14pi))}}}.