Hi everyone,

I wrote this puzzle in my reply to Renouir, but it was lost, since this thread became very big, so I'm starting a new thread for this simple puzzle.

Ok, here it is:

There are 10 wallets with 10 coins in each of them. In one wallet each coin is false, e.g. if true coin weights 1g. (sorry, I use metrics system :)), the false coin weights 0.9g. There is also precise scales. Attention, here is the question: how can you determine the wallet with all false coins in one operation? (You can weight only once).

If this is too simple for you or you know the answer, please, let others think