Da or Ne, and the Gold
On an island of knights (truthful) and knaves (liars), the natives answer yes/no questions with one of two words, "Da" or "Ne", and you do not know which one means yes. You meet a native whose type is unknown and ask him: "If I asked you whether there is gold on this island, would you answer 'Da'?" He replies "Da." Is there gold on the island? Answer yes or no.
Related problems & prerequisites
Worth solving first
- The Alternator Speaks Thrice 6.0/10
- The Spy Who Claimed to Be a Spy 5.9/10
- The Fork in the Road 5.0/10
Source: In the spirit of Raymond Smullyan's knights-and-knaves puzzles and George Boolos's 'Hardest Logic Puzzle Ever' (1996), whose answerers reply 'da' or 'ja'; the embedded-question trick is folklore. Statement written for AxiomIQ.