Two pipes X and Y can fill a tank in 25 hours and 20
hours respectively. Hari opened the pipes X and Y to
fill an empty tank and some times later he closed the
pipes X and Y when the tank was supposed to be
full. After that it was found that the tank was emptied
in 5 hours because an outlet pipe Z connected to the
tank was open from the beginning. If Hari closed the
pipe Z instead of closing pipes X and Y the remaining
tank would have been filled in what time ?

• 
  lcm = 100
  x----4
  y-----5
  x+y = 100/9
  z = 5+100/9 = 145/9
  z in 5 hrs = 5*9/145 = 9/29
  x+y filled 9/29 before they were closed
  rem work =20/29
  time taken for rem work to be done = 20/29*100/9 ~ 7.6
• 7 years agoHelpfull: Yes(0) No(2)