Einstein's Riddle

The story behind Einstein's riddle is that Albert Einstein created it in the late 1800s, and claimed that 98% of the world population couldn't solve it. I am not sure of the true origin, but I have seen this one floating around the internet, and it is a good brain exercise. Here it is:

- In a street there are five houses, painted five different colors.

- In each house lives a person of different nationality

- These five homeowners each drink a different kind of beverage, smoke different brand of cigar and keep a different pet.

Einstein's riddle is: Who owns the fish?

Necessary clues:

1. The British man lives in a red house.
2. The Swedish man keeps dogs as pets.
3. The Danish man drinks tea.
4. The Green house is next to, and on the left of the White house.
5. The owner of the Green house 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 center house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the one 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 Blends smoker lives next to the one who drinks water.

The World's Hardest Riddle?

Some have claimed this to be the worlds hardest riddle. It isn't. It is a decent riddle, though, and a fun one for those who like riddles with systematic solutions. My own solution is below.

A chart seems like the most useful tool to help solve this riddle: Five columns for the five houses, and five rows for nationality, house color, type of drink, type of cigar, and finally, pets. Clue #8 states the man in the middle house drinks milk, so we can start by filling in that one of the 25 boxes created.

Then we deduce as much as possible from each clue. The Norwegian living in the first house (# 9) could mean the first on the left or the right, since it isn't specified. I assume the left (first on chart) for now. Often, with riddles or puzzles, it is faster to make an assumption and if it doesn't work out go back and try the other way, rather than trying to hold open both possibilities while analyzing the other clues.

Clue# 14 says the Norwegian lives next to the blue house, so we can fill in the house color in the second column.

Clue # 4 tells us that the green house has to be in the 3rd or 4th column, since the white house is to the right of it, and that now only works in one of these two positions. However, since clue # 5 says that the owner of the green house drinks coffee, and the milk is the drink of the third house, that means the 4th house is green, the fifth white, and of course, coffee is drunk in the 4th. We can fill in 3 more boxes.

Clue #1 says the British man is in the red house, and the third house is the only one that has neither color nor nationality specified yet, so we can fill in those two boxes. This also gives us the color of the first house, since only yellow is left. Yellow smokes Dunhill (#7), so we get that too.

Horses are next to the Dunhill smoker (#11). The "Blends" smoker lives has a water-drinker to either side (#15), which,looking at the chart now, means in the 1st or 2nd house. Since he also lives next to cats (#10), and horses are in the 2nd house, he has to be in the 2nd, and cats have to be in the 1st, along with a water drinker. The first column is now complete.

The blue master smoker drinks beer (#12), so since two drink boxes are open, but the 2nd house has a Blends smoker, the 5th house has to have the blue master smoking beer drinker.

The Danish man drinks tea (#3), which puts him and his tea in the only house without a drink box filled in; the 2nd.

The German smokes Prince (#13), and only the 4th house has columns open for nationality and cigar type, so we can fill those in. That also leaves only the Swedish man to inhabit the 5th house, and we know that the Swede owns dogs (#2). This is how the chart now looks:

Now, since clue # 6 says the person who smokes Pall Mall rears birds, and the 3rd house is the only place left for Pall Malls, it must also be for the birds. That, of course, leaves only one box unfilled, that of the pet in the 4th house. Thus, the coffee-drinking, Prince Cigar-smoking German in the green house owns the fish in Einstein's riddle.

This is my own way of figuring it out, and I am sure there are other ways to arrive at the answer. It is a fun puzzle, and particularly good for practicing logical reasoning. This makes it worthy of our time whether or not this is truly Einstein's riddle.

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