The Grey Labyrinth is a collection of puzzles, riddles, mind games, paradoxes and other intellectually challenging diversions. Related topics: puzzle games, logic puzzles, lateral thinking puzzles, philosophy, mind benders, brain teasers, word problems, conundrums, 3d puzzles, spatial reasoning, intelligence tests, mathematical diversions, paradoxes, physics problems, reasoning, math, science.


Einstein's Challenge

Quite a number of people have written in asking for the solution to a puzzle called "Einstein's Challenge". It is a fairly difficult logic puzzle, so I decided to post it for everyone. This puzzle is typically prefaced with a note explaining that it was written by Einstein in the last century (i.e., the 19th century) and that he claimed only 2% of the world's population could solve it. This story is likely apocryphal, and certainly more than 2% of all people could solve it, given enough time. Hopefully this won't detract from your enjoyment of it:


  1. There are five houses in five different colours.
  2. In each house lives a person of a different nationality.
  3. These five owners drink a certain beverage, smoke a certain brand of
    cigarette and keep a certain pet.
  4. No owners have the same pet, smoke the same brand of smoke or drink
    the same drink.


  1. The Brit lives in the 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 green house owner drinks coffee.
  6. The person who smokes Pall Mall rears 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 Blue Master drinks beer.
  13. The German smokes Prince.
  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 OWNS FISH?

And for extra points:

Could the claim that Albert Einstein authored this puzzle last century be true?

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