Pipe V1 can fill an empty tank in 8 hours. Pipe V2 can fill the same tank in 16 hours. Pipe V3 can empty the same, completely filled, tank in 12 hours. If three pipes are opened simultaneously, then in how much time will the tank get completely filled?

$\frac{48}{5}$ hours

V1+ = 8 hrs, V2+ = 16 hrs, V3- = 12 hrs,

⇒ Time required for V1 + V2 + V3  to completely fill the tank = \(\frac{48}{6+3-4}\) hrs. = \(\frac{48}{5}\) hrs.