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?

• (x/42) - (x-12)/30 + (x-18)/35 =1 ,
  So, after solving x we get,
  
  x=58.5 Ans.
• 11 years agoHelpfull: Yes(41) No(2)
• 12/42 + 6/42 - 6/30 + x/42 + x/35 - x/30 = 1
  answer is 40.5
• 11 years agoHelpfull: Yes(29) No(9)
• let us assume that A,B and C have 210 units (L.C.M of 42min,30 min and 35 min =210)
  now,
  to do the work alone A will fill the tank at the rate of 210/42 =4units/min
  similarly
  b alone would empty 210/30=7 units/min and
  C will fill the tank at the rate of 210/35 = 6 units/min
  first of all pipe A is opened for 12 min,therefore it does 5x12=60 units of work
  further pipe B is opened and A and B both work together for 6 min so they will together work as -6x2=-12 units,
  so at this point C is also opened...finally all of them will fill the tank at the rate of 4 units/min
  the tank is filled to 60-12 units=48 units,before C was opened therefore all of them will work for filling the tank (210-48)=162 units
  therefore to fill 162 units @4 units it will take 162/4=40.5 min
  therefore the time taken to fill the tank completely will be from the start,i.e.
  12+6+40.5=58.5
• 11 years agoHelpfull: Yes(10) No(1)
• 58.5 min
  
• 11 years agoHelpfull: Yes(6) No(3)
• the answer is 32min.
• 11 years agoHelpfull: Yes(3) No(5)
• Ans will be 6+12+32=50.
  Water filled first inlet pipe= (1/42)*12=2/7
  Water drained by first outlet pipe=(1/30)*6=1/5
  Quantity of water left in tank = 2/7-1/5=3/35
  
  Amount left to be filled= 1- 3/35=32/35
  
  Now part of tank filled by second inlet pipe in 1 min =1/35
  32/35 part will be filled in (32/35)*35=32 min
  Hence total time taken=50 min
  
  
• 11 years agoHelpfull: Yes(0) No(8)
• l.c.m of 42, 35, 30 is 210
  let there be 210 units of work to be done
  then A can fill a tank in 1 min=5 units
  then B can empty the tank in 1 min=7 units
  then C can fill the tank in 1 min=6 units
  initally a started for 12 min= 12*5=60 units of tanks filled
  then (a+b) started for 6 min =(5-7)*6= (-2)*6= -12 units(negative work done)
  therefore remaining work=(210-(60-12)) units= 162 units
  then (a+b+c) will complete in =(162/(5-7+6))=40.5 min
  
• 11 years agoHelpfull: Yes(0) No(0)