In a certain circle, the numerical sum of the area and the circumference is 360 pi, how long is a radius of this circle

Question

I need the radius of this circle. 

Answer 1

πr² + 2πr = 360π

 

  r² + 2r - 360 = 0

 

  (r+20)(r-18) = 0

 

  r = -20 or 18

 

Since r can't be negative, r = 18.