A circular swimming pool is surrounded by a 10 m concrete walk feet wide. If the area of the walk is 11/25 of the area of the pool. Then the radius of the pool in feet is
a. 50
b. 30
c. 16
d. 20

• let radius of pool be =r m,
  area of wall= pi*(r+10)^2-pi*r^2= pi*[(r+10)^2-r^2]
  
  given, pi*[(r+10)^2-r^2] = (11/25)*pi*r^2
  => (100+20r)*25 = 11r^2
  => 11r^2-500r-2500=0
  => 11r^2-550r+50r-2500= 0
  => 11r(r-50)+50(r-500)=0
  => (11r+50)(r-50)=0
  => r= 50 m
  a.50
• 10 years agoHelpfull: Yes(19) No(1)
• let radius of pool be =r m,
  area of wall= pi*(r+10)^2-pi*r^2= pi*[(r+10)^2-r^2]
  
  given, pi*[(r+10)^2-r^2] = (11/25)*pi*r^2
  => (100+20r)*25 = 11r^2
  => 11r^2-500r-2500=0
  => 11r^2-550r+50r-2500= 0
  => 11r(r-50)+50(r-500)=0
  => (11r+50)(r-50)=0
  => r= 50 m
• 10 years agoHelpfull: Yes(4) No(0)
• let radius of pool be =r m,
  area of wall= pi*(r+4)^2-pi*r^2= pi*[(r+4)^2-r^2]
  
  given, pi*[(r+4)^2-r^2] = (11/25)*pi*r^2
  => (16+8r)*25 = 11r^2
  => 11r^2-200r-400=0
  => 11r^2-220r+20r-400 = 0
  =>(11r+20)(r-20)=0
  => r= 20 m
  
  d.20
• 10 years agoHelpfull: Yes(3) No(7)
• 50 is answer
• 10 years agoHelpfull: Yes(1) No(1)
• 50 is the correct answer...
  pi*(R^2-r^2)= 11/25*(pi* r^2)
  R^2*pi = 36/25* (pi*r^2)
  R/r = 6/5
  now R= r+10
  so,
  r+10/r=6/5
  5*r+50=6*r
  r=50
  
  So there you go 50 is the correct answer.
• 10 years agoHelpfull: Yes(1) No(0)
• plz giv me the correct solution. Is it 20 or 50?
  
• 10 years agoHelpfull: Yes(0) No(1)
• radius of pool =r ft,
  concrete walk wide =10m =33ft,
  area of wall = pi*[(r+33)^2-r^2]
  given,pi*[(r+33)^2-r^2] =11/25(pi*r^2)
  by solving above eqn,
  r=16 ft
  
• 10 years agoHelpfull: Yes(0) No(3)
• 50 because it is circular
• 9 years agoHelpfull: Yes(0) No(0)