Below is a riddle claimed to have been composed by Einstein as a boy. Although sometimes, Lewis Carrol is also associated with it. Yet there are no evidence that either of them actually drafted it. Anyhow, it's fiendishly clever and is well-known as "Einstein's riddle".
FACTS: 1. There are 5 houses in 5 different colours. 2. In each house lives a person with a different nationality. 3. These 5 owners drink a certain beverage, smoke a certain brand of cigarette and keep a certain pet. 4. No owners have the same pet, brand of cigaratte, or drink.
CLUES: 1. The Brit lives in a red house 2. The Swede keeps a dog 3. The Dane drinks tea 4. The green house is on the left of the white house. 5. The green house owner drinks coffee. 6. The person who smokes Pall Mall keeps birds. 7. The owner of the yellow house smokes Dunhill. 8. The man living in the house right in the center drinks milk 9. The Norwegian lives in the first house. 10. The man who smokes Blend lives next to the one who keeps cats 11. The man who keeps horses lives next to the man who smokes Dunhill 12. The owner who smokes Camel drinks beer 13. The German smokes Marlborough. 14. The Norwegian lives next to the blue house 15. The man who smokes Blend has a neighbour who drinks water.
The question is, who keeps the fish?
If patience escapes you, check this out--- PoETheeds' video, which takes you through the process of solving it step by step.