2 pipes can separately fill a cistern in 6 & 7 minits resp. if the taps are opened turn by turn each for one minit, find the time taken by them to fill the cistern.
5min , 5 2/3 min , 6 3/7 min , 6 1/4 min , 3 min

• 6 3/7 min.
  
  In 2 minutes cistern filled=(1/6)+(1/7)=13/42
  So upto 6 minutes it will be filled 3*13/42=13/14, remaining=1/14
  Now again the first pipe will fill the remaining in (1/14)/(1/6)=3/7 min.
  So total time taken=6 +3/7 min.
• 9 years agoHelpfull: Yes(1) No(1)
• Total work is 42.In 2 days they can do 13 work.in 6 days they do 39 work.remaining work will be done in 3/7day by a.
• 8 years agoHelpfull: Yes(0) No(0)
• ans: 6 3/7
• 7 years agoHelpfull: Yes(0) No(0)
• ANS- 6 3/7 min
  
  LCM of 6 and 7 is 42 and thus cistern capacity is 42
  in 1 min 1st pipe can fill 42/6=7 and 2nd pipe can fill 42/6=7 and thus in 2 min both pipe can fill 13
  so in 3 cycle it can fill 13*3=39
  Here 3 cycle =6 min because each pipe are opened 1 by 1 for 1 min , thus remaining=42-39=3 which is filled by 1st pipe whose efficiency is 7 for 1 min
  therefore, ans=6 3/7 min
• 7 years agoHelpfull: Yes(0) No(0)