These problems relate to objects of different weight, and using a balanced scale to determine the odd item, be it a false coin, or an under-filled sack of grain. (Usually it's coins though)
The classical problem of eliminating a false coin out of 12 given can be solved using three steps of weighing by a simple level-balance, even without prior knowledge of the false coin being heavier or lighter than the standard coins.
Solve the same problem for 13 coins (i.e. 12 normal, one false , 3 steps to establish which is the different one and whether it is lighter or heavier), provided you may use a balance-scale with non-equal arms.
Latest: 
