



 
Hi Delian, I can help you get started. Divide the 12 coins into three groups with 4 coins each. Call them the red group, he blue group and the green group. Balance the 4 red coins against the 4 blue coins. If they balance you know that the odd coin is one of the green coins. In this case balance one red and one green against 2 green coins. Can you see how to proceed?  


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