Question 837955
You say, by description, {{{pi*(R+1)^2=100*pi}}}, and you originally had {{{pi*R^2=A}}};
You are taking A as a constant.


?
{{{(R+1)^2=100}}}, taking the increased radius equation and dividing left and right sides by {{{pi}}}.
{{{R+1=10}}},
{{{highlight(R=9)}}}-----DONE.