. Pipe A can fill an empty tank in 5 hours and pipe B in 7 hours. If both the pipes are opened together and after 1 ½ hours pipe B is closed, how much time A will take to fill the remaining tank?

• 17/7 hours
  (A+B) 1 hr=1/5+1/7=12/35, so (A+B) 1 1/2 or 3/2 hr=(12/35)(3/2)=36/70=18/35
  Remaining 1-18/35=17/35, which is to be filled by A @ 1/5 per hour
  So time taken to fill remaining tank=(17/35)/(1/5)=17/7 or 2 3/7 Hours
  
• 11 years agoHelpfull: Yes(1) No(0)
• A can fill an empty tank in 5 hours
  B can fill an empty tank in 7 hours
  B did it's work for 3/2 hours
  A did it's work for x+3/2 hours where x is the time taken by A to fill the remaining tank alone
  hence,
  (A did)/(A can) + (B did)/(B can) = 1
  (x+3/2)/5 +(3/2)/7 = 1
  (2x+3)/10 + 3/14 = 1
  (2x+3)/10 = 11/14
  14x + 21 = 55
  14x=34
  x=34/14
  x=2 3/7 hours
• 11 years agoHelpfull: Yes(0) No(0)