Brain Teaser No : 00206

Puzzle Question:

A tank can be filled by pipe A in 30 minutes and by pipe B in 24 minutes. Outlet pipe C can empty the full tank in one hour and twenty minutes.
If the tank is empty initially and if all the three pipes A, B and C are opened simultaneously, in how much time will the tank be full?

Answer --

Solution of Puzzle:

The tank will be full in 16 minutes.
In one minute,
pipe A can fill 1/30 part of the tank.
pipe B can fill 1/24 part of the tank.
pipe C can empty 1/80 part of the tank.
Thus, the net water level in one minute is
= 1/30 + 1/24 - 1/80
= 15/240 part of the tank
Hence, the tank will be full in 240/15 i.e. 16 minutes.

Toughness:

Intermediate