You are presented with three treasure chests, one containing gold coins, one containing silver coins and one containing a mixture of gold coins and silver coins. The three chests are labelled "Gold Coins", "Silver Coins" and "Gold and Silver Coins".
The problem is that all of the treasure chests have been labelled incorrectly.
By opening just one treasure chest how can you determine the contents of all three chests?
Open the treasure chest labelled "Gold and Silver Coins".
If it contains gold coins the treasure chest labelled "Gold Coins" must contain silver coins, and the treasure chest labelled "Silver Coins" must contain gold and silver coins.
Likewise, if it contains silver coins the treasure chest labelled "Silver Coins" must contain gold coins, and the treasure chest labelled "Gold Coins" must contain gold and silver coins.
ALL of the treasure chests are incorrectly labelled.