A friend of mine recently forwarded me the following puzzle, which I have since come across several times on the web. The puzzle was reportedly written by Albert Einstein, who allegedly claimed that it could only be solved by the top 2% of the population. While the stuff about Einstein is almost certainly rubbish (simply because some of the brands of cigarettes referred to in the problem didn’t exist at the time Einstein allegedly wrote the problem), and I’m certain that given enough time most people could solve it, it’s a fun problem nonetheless, so I post it here for your problem solving pleasure.
There are 5 houses of 5 different colours. Each house is occupied by a man of different nationality. The 5 owners each drink a different type of beverage, smoke a different brand of cigar, and keep a different pet. The question is “who owns the fish?”.
The clues are as follows:
- The Brit lives in the red house.
- The Swede keeps dogs as pets.
- The Dane drinks tea.
- The green house is on the left of the white house.
- The green house’s owner drinks coffee.
- The person who smokes Pall Mall rears birds.
- The owner of the yellow house smokes Dunhill.
- The man living in the center house drinks milk.
- The Norwegian lives in the first house.
- The man who smokes Blends lives next to the one who keeps cats.
- The man who keeps the horse lives next to the man who smokes Dunhill.
- The owner who smokes Bluemasters drinks beer.
- The German smokes Prince.
- The Norwegian lives next to the blue house.
- The man who smokes Blends has a neighbor who drinks water.
For the answer visit the comments below.
17 thoughts on “Einstein’s puzzle”
Answer: The German owns the Fish.
Is this problem equivalent to a specific instance of a 5×5 Sudoku board, using only the numbers 1-5? If so, I wonder which is easier for people to solve.
Yeah, it’s the Deutscher all right.
I believe so Jon. The problem is simply a constaint satisfaction problem, with an essentially identical set of constraints to a Sudoko board. If you’re interested, someone wrote a program to solve the problem, available at http://www.stanford.edu/~laurik/fsmbook/examples/Einstein'sPuzzle.html.
As i suspected I’m not in the top 2% who can figure out this kind of problem. Oh well…
Thanks for a very pleasant distraction from the horrors of PhD work 🙂
Nice puzzle. How long did it take you to solve it?
I’m not sure now. It was a while ago that I did it. But I think perhaps around 10 minutes or so… with pen and paper that is, not in my head.
If the answer is the German owns the fish, then it’s a pretty easy puzzle that most people could do within a few minutes.
A process of elimination assigns the various pets mentioned in the clues to the Dane, the Swede, the Norwegian and the Brit. Because of this one assumes that the German owns the fish, but the puzzle does not indicate that this is so. None of the clues say that any of the owners own a fish. The German might own a bear for all we know.
Who owns the fish?
Lots of people own fish. We can’t assume it is the German. We can’t assume they live in any of these houses.
In school my teacher used to say ‘Constsantinople is a big word but can you spell it?’ This took me ages to figure out. I think Einstein’s puzzle is of a similar ilk. It’s about seeing what’s there and not making any assumptions.
The German Own’s the fish i solve it in 4 hour
I was at work in the ER when I solved it (thus a few interuptions): 2 hours. Afterward I emailed both puzzle and solution to family and friends.
Glad you enjoyed it. Hope your friends like it too.
Hi my name is Amanda. I recieved this from a friend and decided to try it out. The best way i could work it out was via a table. Tell me what u think.
Colour Yellow Blue Red Green White
Nationality Norwegian Dane Brit German Swede
Beverage Water Tea Milk Coffee Beer
Cigarette Dunhill Blend Pall PrincessBlue
Pet Cats Horse Birds Fish Dog
Hi Amanda. I also worked this one out using a table, which I gradually filled in and made notes on as I went through and eliminated possibilities based on the constaints.
I solved it in about 20mins. I found that I had to use a 5×5 grid and fill in the known info (2nd house blue) and negative info (ie 2nd house notBrit). Once you have the color order most of it falls into place.
It also helps to have a list of all the category items.
Please be noticed ,gentlemen.
The clue No. 4 says “The green house is on the left of the white house. “.
It doesn’t necessarily means the green house is next to the white one.
In this case. The answer is more than one.
I am from China. I also worked out the German keeps fish at the beginning. That’s why I want to find the original words in the puzzle.
I also used the grid method although mine was a 5 x 6 grid taking into consideration the house number. a few minutes later reasoning determines the German owns the fish.
However I love the “out of the box” thinking displayed my some of the responders here. Very early on I considered that the houses were not necessarily in a straight line and that maybe they formed a circle. I also wondered from who’s perspective the right and left were as well as the possibility as mentioned above that left did not necessarily mean next door and that in fact left could in fact mean right at the same time as it meant left in the case of my circle theory.
The idea proposed by John Nelson above is not one I considered but I enjoyed the thought processes involved.
In the end I think the part that intrigued me most about this problem is seeing how different brains function as witnessed by the various responses here.
I also learnt a little something new about my own brain because the whole time I was doing the puzzle I was internally viewing much of the info as small pairs of boxes (ie swede and dogs) which then needed to fit into my grid in much the same way that bits fit together in tetris.
So in effect I was not only deciphering the clues but also searching for a quicker method whereby patterns would match.
I have no idea if that makes sense to anyone but the realisation of what I was doing has fascinated me somewhat.