I found this on some high schooler's blog who claimed Einstein said that 98% of the world's population couldn't solve this puzzle. That's silly, unless he just meant that because most people can't speak English. Anyway, you can try your hand on it. I figured it out in 10 minutes, but it's 10 minutes straight of work, and it is kind of hard to keep track of all the information in your mind during that time. So I used notepad. Maybe that's cheating, and that's why it's considered so hard, because I would have a really hard time doing it all in my head. You can post in the comments if you solve it. I think there's room if you use abbreviations. I haven't seen any answers, myself, though, so we can argue about it if you think I'm wrong on something. I'll post the answers if anybody replies.

I take it as an implicit premise that the houses are lined up on one side of the street.

On a street, there are 5 houses painted 5 different colors. In each house lives a person of different nationality. These 5 people each drink a different beverage, smoke a different brand of cigar, and keep a different pet.

Question: Who owns the fish?

Hints:

1. The Briton lives in a red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the left of the white house.
5. The owner of the green house drinks coffee.
6. The person who smokes Pallmall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The man living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the man who keeps cats.
11. The man who keeps horses lives next to the man who smokes Dunhill.
12. The man who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The man who smokes Blends has a neighbor who drinks water.