Two water pipes are used to fill a water tank. The first pipe alone can fill the tank in 7 hours, and the second pipe alone can fill the tank in 14 hours. If both pipes are used for the first 4 hours, and then the first one is shut off, how long, in hours, will it take for the second pipe to finish the job ?

• second pipe will take two more hours.
  both pipes will complete 12/14th portion in 4 hours.
  remaining 2/14th portion will filled in 2 hours by second pipe.
• 11 years agoHelpfull: Yes(1) No(0)
• 2hrs
  
  bcuz 2 hr is ryt answer
• 11 years agoHelpfull: Yes(0) No(0)
• ans=2hrs ,let tank can be fill in t min
  as second pipe is open for t time and first pipe is open for 4 hr so
  4/7+t/14=1 ,t=6 hrs ,tank is full in 6 hrs
  so tym taken by second pipe=6-4 =2 hrs
• 11 years agoHelpfull: Yes(0) No(0)