1. A, B and C are pipes attached to a cistern. A and B can fill it in 10 and 15 minutes respectively, While C can empty it in 20 minutes. If A, B and C be kept open successively for one minute each, find the last integral number of minutes required for the cistern to get filled

• 24 min. 40 sec.
  3 min filling=(1/10)+(1/15)-(1/20)=7/60
  So upto 3*8=24th min, cistern filled=7*8/60=56/60=14/15
  Remaining=1/15, which is to be filled by 'A' again
  time taken by A=(1/15)/(1/10)=2/3 min.=40 sec.
  So total time required=24 min+ 40 sec.
• 10 years agoHelpfull: Yes(61) No(16)
• A fill it in 1 min 1/10
  B fill it in 1 min 1/15
  C empty in 1 min 1/20
  In 1 min it is filled if the 3 pipes are open 1/10+1/15-1/20=7/60
  It will be filled in 60/7 min=8.57 min
• 10 years agoHelpfull: Yes(21) No(16)
• work in 3 minutes =1/10 + 1/15 -1/20 =7/60
  thus 7/60 is filled in 3 mins thus 60/7 *3=26mins 11 sec to fill the tank
• 10 years agoHelpfull: Yes(11) No(12)
• A can fill 10% in 1 min, B 6.6% and C can empty 5% in 1 min....altogether 11.6% of work is done in 3 min...so altogether 92.8% work can be done in 24 min and remaining 7.2% work can be done by A in 43 secs....therefore cistern can get filled in 24 min 43 secs.
• 10 years agoHelpfull: Yes(7) No(3)
• A,B,C successively filled 1 min each(total 3min)=(x/10)+(x/15)-(x/20)=7x/60
  After 7*3 min(21min),cistern fill= 49x/60
  After 8*3 min(24min),cistern fill= 56x/60
  After 9*3 min(27min),cistern fill= 63x/60>1
  
  So its filled between 24 and 27,
  Now For 25Th Min, cistern fill= 56x/60+A's filling in 1min=56x/60+x/10=62x/60 >x (So its filled in 25th Min)
  
  So Answer=25min
• 10 years agoHelpfull: Yes(6) No(1)
• 25 is the answer
  
• 10 years agoHelpfull: Yes(4) No(4)
• (1/10) +(1/15) -(1/20)=(1/x)
  =>in 3 min (7/60)of the cistern is filled
  =>1 cistern will need 24min and 40 sec to fill completely
• 9 years agoHelpfull: Yes(3) No(0)
• A does 10% work in 1 minute, B does 6.77% work in 1 minute and C does 5% work in 1 minute(negative work)
  
  now in every 3 minutes % of work done = 10%+6.77%-5%= 11.67%
  now as work is taken for 3 minute basis so..total work required= 3*100%
  therefore time taken = (3*100%)/11.67%= 25.706
  taking only integer part = 25 minutes (answer)
• 10 years agoHelpfull: Yes(2) No(2)
• (1/10) +(1/15) -(1/20)=(1/x)
  =>in 3 min (7/60)of the cistern is filled
  =>1 cistern will need 24min and 40 sec to fill completely
  
• 10 years agoHelpfull: Yes(2) No(0)
• Admin please mark the correct answer.....
  
• 7 years agoHelpfull: Yes(1) No(0)
• a=110 b=115 c=120 (for 1 minute)
  if all the pipes are allowed to do their respective work(i.e a,b=in c=out)
  then,
  1/10+1/15-1/20
  =>14/120(amount filled in 1 minute)
  so,120/4 is the time taken to fill the whole tank
  120/4=30 minutes
• 10 years agoHelpfull: Yes(0) No(12)
• A,B,C successively filled 1 min each(total 3min)=(x/10)+(x/15)-(x/20)=7x/60
  After 7*3 min,cistern fill= 49x/60
  After 8*3 min,cistern fill= 56x/60
  After 9*3 min,cistern fill= 63x/60>1
  
  So its filled between 24
• 10 years agoHelpfull: Yes(0) No(3)
• 25 will be the answer !!!
• 10 years agoHelpfull: Yes(0) No(4)
• 1/10+1/15-1/20=7/60
  1/60/7=8.6
• 10 years agoHelpfull: Yes(0) No(3)
• 1/10+1/15-1/20=7/60
  1/60/7=8.6
• 10 years agoHelpfull: Yes(0) No(3)
• X O I F ?
  a) D b) E c) F d) B
  asked in TECHMAHINDRA
• 7 years agoHelpfull: Yes(0) No(0)