I have three blocks. Two of them are the same weight. The third is a different but unknown weight (it could be heavier or lighter).
Using a balance scale at most two times find the odd block.
(In reply to 2 for the price of 1
by Ady TZIDON)
As any inveterate problem solver knows, this is just a simpler case of the good, old 12 balls problem!
Nice to see it turn up again, in new clothes.