Twenty metal blocks are of the same size and external appearance; some are aluminum
, and the rest are duraluminum
, which is heavier.
Using a pan balance to determine how many blocks are aluminum, what is the minimum number of weighings to be done?
It seems to me that no matter what weighing scheme is used, that the scenario using the most weighings will always be 19 weighings, particularly when a lot of equal weighings occur. Certain weighing schemes will have a lower number of expected weighings, but I think there will always be a scenario requiring 19.