A water tank can be filled by pipe P alone in 30 mins and by pipe Q alone in 20 mins the same tank can be emptied by pipe R in 25 mins. if all the 3 pipes are opened at the same time, how long will it take to fill the water tank?
[A] 12.12 mins
[C] 22.10 mins
[B] 23.08 mins
[D] 30.15 mins

• work done by(A+B+C) in 1 hr=1/30+1/20-1/25
  =13/300
  so time required to fill the tank=300/13=23.08
• 11 years agoHelpfull: Yes(11) No(2)
• p=30
  q=20
  r=25 perday work p=10,q=15,q=-12(because it's empty the tank so negative sign)
  300/13=23.08min's
• 10 years agoHelpfull: Yes(0) No(0)