A cistern can be filled by pipes A, X in 3 minutes 45 seconds. If the larger pipe takes 4 minutes less than the smaller pipe to fill the cistern, how much time will the smaller pipe take to fill the tank?
A. 12min
B. 6min
C. 10min
D. 8min

• let A is larger pipe and X is smaller then,
  let time taken to X = t
  then time taken to A= t-4
  so efficiency of X=t-4
  and efficiency of A=t
  using formula time= total work/total efficiency
  total work =t(t-4)
  total time= 3 + 45/60= 15/4
  using formula
  15/4=t(t-4)/(t+t-4)
  by solving it
  t=10 min
  so smaller pipe take 10 mins.
  
• 11 years agoHelpfull: Yes(15) No(3)
• 1/t+1/t-4=1/3.75
  2t-4/t^2-4t=4/15
  4t^2-46t+30=0
  t=10 bcz t can't be .5
  
• 11 years agoHelpfull: Yes(8) No(1)
• let A is larger pipe and take x minute and X is smaller and take y minute
  then 1/(1/x + 1/y) = 15/5......(1)
  and x + 4 = y............(2)
  solving (1) and (2)
  x = 6 , y = 10
  so y= 10 is the required answer
• 11 years agoHelpfull: Yes(2) No(1)
• larger pipe fill in =xhr(let)
  so, smaller= x-4 hr.
  acording to qstn.
  (x(x+4))/x+x+4=(15/4)minute
  solve u get x=6 so smaler will take 6+4=10hr.
  
• 11 years agoHelpfull: Yes(1) No(1)