Two pipes can fill a tank in 6 hours and 8 hours respectively. A third pipe can empty the same tank in 12 hours. If all the pipes start working together, how long it will take to fill the tank?

Question	Two pipes can fill a tank in 6 hours and 8 hours respectively. A third pipe can empty the same tank in 12 hours. If all the pipes start working together, how long it will take to fill the tank?
Type	multiple_choice
Option	4 hours	incorrect
Option	4.5 hours	incorrect
Option	4.8 hours	correct
Option	5.2 hours	incorrect

Part of the tank filled by two pipes in one hour = 1/6  + 1/8

Part of the tank emptied by the third pipe in one hour = 1/12

∴ Net part of the tank filled in one hour =  1/6 +1/8  – 1/12

5/24 Part of tank can be filled in one hour

∴ The whole tank will be filled in  24/5  = 4.8 hours