The Problem: "Einstein"'s 15 relations problem

• The Englishman lives in the red house.
• The Swede keeps dogs.
• The Dane drinks tea.
• The green house is just to the left of the white one.
• The owner of the green house drinks coffee.
• The Pall Mall smoker keeps birds.
• The owner of the yellow house smokes Dunhills.
• The man in the center house drinks milk.
• The Norwegian lives in the first house.
• The Blend smoker has a neighbor who keeps cats.
• The man who smokes Blue Masters drinks bier.
• The man who keeps horses lives next to the Dunhill smoker.
• The German smokes Prince.
• The Norwegian lives next to the blue house.
• The Blend smoker has a neighbor who drinks water.

Question: Which person has fish?

Click here for a solution.

A quick note about this problem: So I keep seeing this described as one of the "Einstein" problems, usually with some bogus claims that only 2% of the population can solve this type of problem. As for authorship, I am guessing that some time in the distant past someone slapped Einstein's name on the riddle as a bit of salesmanship and now no one can absolutely refute the claim.

As for the 2% claim, that is just bogus. The appearance of difficulty is generate by people not periodically backing up their reasoning state, and the steps they followed. As a result if they make any mistakes they either need to start over from the beginning or give up on the problem. Given that this is a time consuming problem to solve, most people probably eventually just give up. All the reasoning is fairly simple; it is the mechanics of the reasoning that can get unwieldy.

Seriously, just take notes as you go along sufficient for you to back track and find your errors. Then the problem is straight forward and easy to solve.