) A circular swimming pool is surrounded by a concrete wall 4 feet wide.if the area of the wall is 11/25 of the area of the pool, then the radius of the pool in feet is?

• Let radius of the pool be r.
  Now radius of wall built around is r+4.
  Area of pool=πr^2.
  Area of wall= π(r+4)^2-πr^2.
  Therefore,
  11/25 *πr^2= π(r+4)^2-πr^2.
  After solving we get......
  11r^2 -200r-400=0.
  We get value of r= 20 feet.
• 9 years agoHelpfull: Yes(15) No(4)
• According to the question,
  Let r be the radius of the pool
  then the radius including the wall is r+4 feet
  so the area of the pool is pi*r*r feet.squares
  but the area of the concrete wall will be,
  { pi*(r+4)*(r+4) - pi*r*r } feet.squares.
  now according the question,
  { pi*(r+4)*(r+4) - pi*r*r } = 11/25*pi*r*r
  solving this we get,
  the value of r is 2 feet.
  so the radius of the pool is 2 feet.
• 9 years agoHelpfull: Yes(1) No(3)