I have two sets of 8 coins. In one set the coins weigh 30g each, in the other set the coins weigh 31g each.
Unfortunately they got mixed together in one big pile of 16 coins. I want to identify one coin. It can be from either set.
(Easy) Using a balance scale, identify a coin in four weighings.
(Hard) Identify a coin in just three weighings.
I haven't played with this, but the easy method is pretty clear. I don't offhand see the hard method.
The easy method is "superior" in that:
a) It is simpler to do
b) The expected number of weighings with the easy method is lower