A circular swimming pool is surrounded by a concrete walk 4 feet wide. It the area of the walk is 11/25 of the area of the pool, then the radius of the pool is
A. 8 [DCRU]
B. 20
C. 16
D. 30

• B. 20
  
  If radius of the pool=r, so total outer radius including concrete walk=r+4
  Area of the walk=Pi*(r+4)^2 - Pi*r^2=8*Pi*(r+2)
  Given Area of the walk=11/25*Area of the pool, 8*Pi*(r+2)=(11/25)*Pi*r^2 or
  11r^2-200r-400=0
  (11r+20)(r-20)=0
  So r=20
• 9 years agoHelpfull: Yes(2) No(2)