You have nine brass rings, but three are actually gold. Can you pick these out using a balance scale three times at the most?

(In reply to The answer is ... by Charlie)

I had in mind something like this:
and, while I have presupposed the Gold rings, in practice that would not be so - it was just help my thinking.

I divide the rings into 3 groups.  GroupA and GroupB are on the scales while GroupC in on the table. For each weighing I rotate just 'place'.
Test#   GroupA   GroupB    GroupC   Result
  1       G 2 3      4 G 6      7 8 G      Equal - Table has either 1 or 3 G
  2       G G 2     3  4 G     6 7 8      Heavy L - Table 0 or 2 G
  3       8 G G     2  3 4     G 6 7      Heavy L - Doubt that I could tell further.

Think that I might have to concede in Charlie's favour.

Posted by brianjn on 2005-06-24 06:35:06