Two pipes P and Q fills a tank in 30 and 60 min. a person starts that at 5am to fill. he comes when it may fill but he saw that pipe R was also opened which empties that tank. Then he closes R. Now 20 min takes to fill the tank. What time R takes to empty the tank?

• P fills 1/30 in 1 min and Q fills 1/60 in 1 min
  so 1/30 + 1/60 = 1/20 fills in 1 min
  so tank fills in 20 min
  after he close R it takes 20 min to fill so the tank is empty when he come
  so r takes 20 to empty the tank.
• 11 years agoHelpfull: Yes(15) No(3)