Two pipes can fill a tank in 10 and 12 hours, while third pipe will make the tank empty in 20 hours. If all three pipes operate simultaneously. In how many hours the tank will be filled ?

• ANSWER : 7.5 hours
  
  SOLUTION :
  
  In 1 hour it fill 1/10 + 1/12 - 1/20 = 8/60
  So fill tank fillup in 60/8 = 7.5 Hours
• 13 years agoHelpfull: Yes(50) No(1)
• l.c.m of 3 pipes is(10,12,20) is 60
  
  efficiency of pipe a is 60/10=6
  efficiency of pipe b is 60/12 =5
  pipe c is 60/20 =3
  
  so a=6
  b=5
  c=3
  
  (filling pipe - empty pipe)
  that is 6+5-3=8
  
  then 60(l.c.m)/8
  60/8=7.5 hrs
  correct ans is 7.5
• 9 years agoHelpfull: Yes(7) No(0)
• In 1 hour it fill 1/10 + 1/12 - 1/20 = 8/60
  So fill tank fillup in 60/8 = 7.5 Hours
• 10 years agoHelpfull: Yes(6) No(0)
• in one hour the tank will be filled by a fraction given by (x/10+ x/12- x/20) i.e. 0.1333*x
  hence to fill completely i.e. to get complete 1
  it will take 1/.0.1333 hours
  which is equal to 7.5hrs
• 10 years agoHelpfull: Yes(3) No(2)
• a and b can fill in 10hr and 12hr while c can empty in 20hr..therefore the time taken to fill the tank is,
  LCM of(a,b,c)/(LCM/a+LCM/b+LCM/c)
  240/(24+20-12)
  =7.5hours
• 10 years agoHelpfull: Yes(2) No(1)
• 1/10+1/12=11/60
  11/60-1/20=11-3/60
  8/60=7.5
• 9 years agoHelpfull: Yes(0) No(0)
• answer is 75,
  as Lcm of 10,12,20 is 600 so 1/10 +1/12 -1/20 = 8/600 =1/75
• 9 years agoHelpfull: Yes(0) No(0)
• take +ve for pipes those filling the tank and for emptying take -ve sign to get a correct answer, so
  answer -> time in hours (reciprocal of solution) = (1/10)+(1/12)-(1/20) = 1/7.5, so answer is 7.5 hours.
• 6 years agoHelpfull: Yes(0) No(0)
• 1 pipe=10hr and
  2 pipe=20hr for fill the tank;
  3 pipe =take 20hr for empty tank;
  for 1hr=1/10+1/20-1/20=8/60;
  :1hr=8/60
  ?=1
  =>60/8=?
  ?=7.5hr
• 6 years agoHelpfull: Yes(0) No(0)
• Water filled by pipe 1 in 1 hr = 1/10
  similarly by pipe 2 is = 1/12
  emptied by pipe 3 in 1 hr = 1/20
  where all work simultaneously = 1/10+1/12-1/20 = 16/120 = 2/15
  so, 2/15 part of the tank gets filled in 1 hr
  so 15/2 = 7.5hrs tank takes to get full
• 6 years agoHelpfull: Yes(0) No(0)
• Ans : 12 hr
• 5 years agoHelpfull: Yes(0) No(0)