In what time would a cistern be filled by three pipes whose diameter are 1 cm , 4/3cm, 2 cm running together.. when the largest alone will fill it in 61 minutes; the amount of water flowing in by each pipe being proportional to the square of its diameter?

• ans 36 min;
  (4k+16/9k+1*k)T=C..........(1)
  k:some pipe const same for all
  C:capacity of cistern
  T:required time
  also 4k*61min=C........(2)
  substituting (2)in (1), we get
  T=36min
• 10 years agoHelpfull: Yes(23) No(3)
• For all three pipes together:
  2^2 = 4
  1^2 = 1
  4/3^2 = 16/9
  
  4 + 1 + 16/9 = 61/9 is proportional to the amount of water flowing in.
  
  We know that for the largest pipe: 2^2 = 4 is proportional to the amount of water flowing in and this takes 61 minutes.
  so,
  61 x (4/(61/9)) = 61 x (36/61) = 36 minutes.
• 10 years agoHelpfull: Yes(11) No(0)
• 2cm diameter is largest-------61mins
  larger the diameter lesser the time it takes....
  1cm-------------------61*2^2=61*4=244.
  4/3cm-------------------61*4*3*3/4*4=549/4
  total time taken is 1/61 + 1/244 + 4/549 =36+9+16/61*4*9=1/36..
  36 mins will be taken.
• 10 years agoHelpfull: Yes(2) No(2)
• mr.siripally abinay in the problem it was told that that the square of the diameter is proportional so we have to square that
• 10 years agoHelpfull: Yes(1) No(0)
• Y vivek ?
  Time taken would be inversely proportional to dia^2. Hence I think time taken wud b 1/t=1/61+16/(9*61) + 4/61 = 9 min
• 10 years agoHelpfull: Yes(0) No(3)
• ans will be 9 mins
• 10 years agoHelpfull: Yes(0) No(1)
• SIMRAN will you please tell me why you square the diameter of pipe
• 10 years agoHelpfull: Yes(0) No(0)