Question: There are 3 chests, labelled food, beds and food and beds.True enough, one chest contains only food, one chest contains only beds and one chest contains both. You are warned that the chests' labels may be lying collectively, or not at all. How can you tell which chest contains what by just opening one of them?
Answer: Open any chest. If its content matches its labels, that means the others will also hold their respective content. If any other chest labels are lying, the rest would also have to hold the items that are not on their label.