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.

(In reply to re(3): Short solution. by Jer)

Not quite. in the third round I weighed the leftover 4 against any 4 of the 6, but the idea is the same.  The procedure is hinted at in my last post.

Posted by broll on 2016-01-12 22:14:47