A circular swimming pool is surrounded by a concrete wall 4ft wide. If the area of the concrete wall surrounding the pool is 11/25 that of the pool, then the radius of the pool is? Choose the correct option:
A) 22
B) 20
C) 88
D) 387
E) 19
let the radius of the pool be Rft   Radius of the pool including the wall = (R+4)ft   Area of the concrete wall = {\color{20lack} \Pi \left [ (R+4)^{2} -R^{2}\right ]}={\color{20lack} \Pi \left [ (R+4+R)(R+4-R) \right ] =8\Pi (R+2)} sq feet   {\color{20lack} \Rightarrow 8\Pi (R+2)=\frac{11}{25}\Pi R^{2}\Rightarrow 11R^{2}=200(R+2)}   Radius of the pool R = 20ft   Answer: 20) 20ft
<result>B</result>
A circular swimming pool is surrounded by a concrete wall 4ft wide. If the area of the concrete wall surrounding the pool is 11/25 that of the pool, then the radius of the pool is?