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?

• let after the 3rd inlet is added tank is filled in x min
  so first inlet will work for (x+18) similarly second outlet for (x+6)
  now why 100/42 its because in 42 min it fills 100% so in 1 min 100/42..
  so in (x+18)min it will work (X+18)*100/42
  similarly in (x+6)min second outlet will work (X+6)*100/32
  (x+18)*100/42 - (x+6)*100/30 + (x)*100/35 = 100
  therefore x = 40.5
  so time to fill the tank = 40.5+18 = 58.5
• 11 years agoHelpfull: Yes(16) No(1)
• let a ,b and c pipe
  a can fill the tank in 42 minutes.
  then in 1 minute it can fill 1/42.
  in 12 minute (1/42)*12=2/7.
  next 6 minute a can fill (1/42)*6=1/7
  and b can remove (1/30)*6=1/5
  then in 18 minutes tank filled=2/7+1/7-1/5=8/35
  1-8/35=27/35 remain for filling
  in 1 hr a,b,c can fill
  1/42+1/35-1/30=2/105
  2/105 can fill in 1 minute
  then 27/35 can fill in 40.5 minute.
  18 minute is also then
  40.5+18=58.5 minutes
• 11 years agoHelpfull: Yes(14) No(0)
• x/42-(x-12)/30+(x-18)/35=1.
  4x-24/210=1
  4x-24=210
  4x=234
  x=58.5
• 11 years agoHelpfull: Yes(7) No(0)
• ans is 58.5 min
• 11 years agoHelpfull: Yes(6) No(1)
• ans is 58.5 min.
• 11 years agoHelpfull: Yes(4) No(0)
• let a ,b and c pipe
  a can fill the tank in 42 minutes.
  then in 1 minute it can fill 1/42.
  in 12 minute (1/42)*12=2/7.
  next 6 minute a can fill (1/42)*6=1/7
  and b can remove (1/30)*6=1/5
  then in 18 minutes tank filled=2/7+1/7-1/5=8/35
  1-8/35=27/35 remain for filling
  in 1 hr a,b,c can fill
  1/42+1/35-1/30=2/105
  2/105 can fill in 1 minute
  then 27/35 can fill in 40.5 minute.
  18 minute is also then
  40.5+18=58.5 minutes
• 11 years agoHelpfull: Yes(4) No(0)
• ans. is 58.5 mnts
• 11 years agoHelpfull: Yes(3) No(1)
• A(1st inlet pipe) fills in 42mins so its rate of doing work 100/42= 2.38%
  B(outlet pipe) empties with %age 100/30=3.33%
  
  now A first works for 12mins so %age filled by A is 2.38*12=28.56%
  then it works for 6 mins so %age filled again by A is 2.38*6=14.28%
  
  meanwhile B(outlet pipe)was also working for 6 mins ,
  so its rate of emptying is 3.33*6=19.98%
  
  So net work done till 18mins is (A for 12mins)+(A for 6 min)-(B for 6 min)
  =28.56+14.28-19.98= 22.86%
  so remaining is 100-22.86=77.14%
  
  now A+B+C together fill in 2.38%-3.33%+2.85% i.e. 1.9%
  this 1.9% is filled in 1 min
  so remaining 77.14% will be filled in 77.14/1.9 i.e. equal to 40.6 min
  hence the total time taken will b 40.6+18 i.e. 58.6min
  ans =58.6min
  
  
• 11 years agoHelpfull: Yes(3) No(2)
• is ans = 32 min..............
  verify
• 11 years agoHelpfull: Yes(0) No(4)
• take lcm of 42 min and 30 mn which will give capacity 420liter
  now inlet pipe rate is 10 l/m and out let has 14 l/m so
  inlet opned for 12 minute fill 120 liter and then out let pipe com which out water 14 liter /m then (14-10) i.e 4 liter reduced per minut from 120 liter for 6 minute=24 liter
  120-24=96 liter left
  then another inlet comes whose rate is 324/35=27 minute (420-96=324)
  ans 27 minute
• 11 years agoHelpfull: Yes(0) No(3)
• hey could u please make it clear???
  
• 11 years agoHelpfull: Yes(0) No(0)
• Assume total tank capacity = 210 Liters Now pipe A fill this tank in 210/42 = 5 min B empties this tank in 210 / 30 = 7 min C fills this tank in 210 / 35 = 6 min Assume tank gets filled in x min. So x × 5 - (x-12)×7 + (x - 18) × 6 = 210 ⇒ x = 61.25
• 11 years agoHelpfull: Yes(0) No(0)
• i dun knw. ans to hume na ptaaa
• 11 years agoHelpfull: Yes(0) No(0)