An empty tank be filled with an inlet pipe ‘A’ in 42 minutes. after 12 minutes an outlet pipe ‘B’ is opened which can empty the tank in 30 minutes.
After 6 minutes another inlet pipe ‘C’ opened into the same tank, which can fill the tank in 35 minutes and the tank is filled find the time taken to fill the tank?

• 12[1/42]+6[1/42-1/30]+t[1/42-1/30+1/35]=1
  t=40.5
  After getting the t value, the total time is t= 40.5+12+6.=58.5 mins
  
• 9 years agoHelpfull: Yes(9) No(2)
• let total time be t,
  => (t/42)-[(t-12)/30]+[(t-18)/35]=1,
  solving t=58.5
• 8 years agoHelpfull: Yes(3) No(0)
• A pipe can fill the tank in 1 min=12/42=2/7 part of the tank fill
  Remaining tank to fill=1-(2/7)=5/7
  A and B together fill in 1 min=(1/42)-(1/30)=2/35,in 6min=12/35 part fill, remaining=(5/7)-(12/35)=13/35,A and B and c together fill in 1 min=(1/42)-(1/30)+(1/35)=1/35 part fill then
  3 pipes together fill 13/35 part in 13 min
  So a for 6min
  a-b in 12min
  a-b+c in 13min
  Total=31min
• 9 years agoHelpfull: Yes(1) No(3)
• Assume total tank capacity = 210 Liters
  Now capacity of pipe A = 210/42 = 5 Liters
  Capacity of B = 210 / 30 = - 7 Liters
  Capacity of C = 210 / 35 = 6 min
  Assume tank gets filled in x min after the third pipe got opened.
  So x×5+6×(−2)+4x=210
  ⇒48+4x=210⇒4x=162⇒x=40.5
  Total time taken to fill the tank = 40.5 + 12 + 6 = 51.5
• 8 years agoHelpfull: Yes(1) No(0)
• net working time to fill up the tank while pipe A is active = 42+12 = 54 min
  net working time to empty the tank while pipe B is Active = 30+ 6= 36 min
  fill up time of pipe C is = 35 min
  hence A work at one min = 1/54 , B=1/36 , c= 1/35
  hence three pipes work together in one min = (1/54) - (1/36) +(1/35)=0.01931
  Hence to fill up the tank while three pipes are actives = 1/0.01931= 51.78 mins
• 8 years agoHelpfull: Yes(0) No(2)
• its very simple....let the total volume of tank is 210 litres
  then in 1 min A fill 5 litres , B can empty 7 litres and C can fill 6 litres.......so let x amount of time require to fill the tank.....so A works for x min and B works for (x-12) and C works for (x-30) . therefore
  5x-7(x-12)+6(x-6)=210
  x=40.5 min.
  
• 8 years agoHelpfull: Yes(0) No(0)