Puzzles

Consider this family of popular puzzles:  You have two empty water jugs with no markings.  One holds exactly 8 liters of water when full, and the other holds 3 liters.  You also have a full tub with an endless supply of water and another large unmarked empty jug of unknown volume.  The goal is to measure out a given volume of water to put into the large jug using the other two jugs.