Since there’s still a zebra on the loose in western Washington, I thought I’d try this puzzle that I first solved in high school and have since forgotten about.
Who Owns The Zebra?
There are five houses.
The Englishman lives in the red house.
The Spaniard owns the dog.
Coffee is drunk in the green house.
The Ukrainian drinks tea.
The green house is immediately to the right of the white house.
The Old Gold smoker owns snails.
Kools are smoked in the yellow house.
Milk is drunk in the middle house.
The Norwegian lives in the first house.
The man who smokes Chesterfields lives in the house next to the man with the fox.
Kools are smoked in the house next to the house where the horse is kept.
The Lucky Strike smoker drinks orange juice.
The Japanese smokes Parliaments.
The Norwegian lives next to the blue house.
This part is easy:
The Norwegian lives in the first house, and he lives next to the blue house. So the Norwegian can’t live in the blue house and the blue house is the second house.
The 1st house can’t be red, because the Englishman lives in the red house; nor can it be white or green, because those are next to each other. Therefore, the fist (Norwegian’s) house must be yellow.
Kools are smoked in the yellow house, which is house #1, which is where the Norwegian lives.
The horse owner lives in the house next to the Kools smoker, so the horse lives in house #2, the blue house.
After that, I just made some guesses and applied the clues until I got the answer:
The Japanese owns the zebra, and the Norwegian drinks water.
Is there a more logical method than just making a guess and then working with it?
Could you spoiler the steps you took to get to the answer, in addition to the answer?
I remember doing this puzzle back in high school also, and I solved it. But that was so long ago, that I had forgotten about it until you mentioned it just now. I’d like to try it again.
The un-spoilered part is easy enough that I didn’t think it needed spoilering.
For the rest, I made assumptions and looked to see if any of the assumptions were contradicted by other clues, I wonder if there is a more elegant – logical – procedure to derive the answer without making guesses.
sy part.
I think that’s what I did, but my spreadsheet started with assumptions after th initial easy part.
The first clue gives you the size of the grid, categories are nationality, house color, house order, beverage, pets, and cigarette brand. So, for instance, the grid that crosses nationality and house color establishes that “The Englishman lives in the red house”, so you can eliminate all of the squares with anyone else in the red house and the Englishman in any other color of house and so forth. As you keep on blocking out connections you end up with more exclusions until you get down to some reduced set of explicit connections, and then can use the positional arguments such as “The man who smokes Chesterfields lives in the house next to the man with the fox” to further eliminate possibilities until you exhaust all possible options except the unique ones.
One problem is that you don’t have enough info. You are only told about someone drinking milk, coffee, tea, and orange juice. There is no way to discern what the final household drinks – could be whisky, could be iced tea, could be a thousand things. I think you must have left out at least one clue.
This is quite literally a sparse matrix which can be reduced by exclusion. The relational arguments are the most challenging to evaluate, e.g. “The man who smokes Chesterfields lives in the house next to the man with the fox.” But just working with the explicit definitions and eliminating impossible combinations will reduce the number of combinations to just a few, and then you can work through the positional logic, i.e. whose house is next to whose to work through the four relational statements.
It is water (parenthetically) but you don’t need that explicitly defined; as you have five categories of everything, it could just be Irish whiskey for all that it matters. Ditto for the fifth animal (a zebra).
My mother saw a version of this in Reader’s Digest, of all places (must’ve been in a doctor’s waiting room where it was the only thing to read; she considered it declassé), in the mid-1960s, and she and my sister and I solved it together.
But it was definitely a different version because I remember that figuring out that the Englishman lived in the red house was the key step to solving the rest of the puzzle.
I don’t recall being taught how to populate a matrix in high school. I kind of remember doing something with matrices in my BASIC programming class the first semester of college, but that was a long time ago. The memory is as dim as the dying dot when you turned off a tube television. (Dot? Matrix? ) So after the first bit, I guessed.
In Excel, I called the first column House 1, House 2, House 3, House 4, and House 5, leaving column A blank. In column A, below the house headers, I put Colour, Nationality, Pet, Drink, and Cigarette. I deduced the information stated in the OP, highlighting ‘Norwegian’, ‘Blue’, and ‘Milk’ in yellow, and using red font for ‘Yellow’, ‘Horse’, and ‘Kools’.
That’s where the guessing started. The white and green houses could be House 3 and 4, or House 4 and 5. I randomly assigned them House 4 and 5, and assigned Red to House 3. From there I went down the list of clues, randomly putting the information in until I came upon an impossibility. When I did, I backed up and tried different positions until I found the solution. Had I not found the solution, I would have swapped the positions of the Red, White, and Green houses and done the same thing. (i.e., I was lucky I guessed right at the start.) It worked, but it feels like there’s a smarter way of doing it.
An elimination matrix has a specific configuration.
You assign the first category a the first row, with entries for each element. Then you list the remaining categories as columns across, with a line for each item of each category.
Then you take the third, fourth, fifth etc category and list them as rows below the first category, in reverse order.
Then you block out the lower right sections as duplicates. Now you have an elimination grid where every item in every category can be matched to every other one.
Then mark all the given yes with a dot or circle. All yes marks mean the rest of that row and column in that category match can be marked out, say with an x.
Mark any other given nos.
Now you can cross reference between categories, looking for eliminations until you find what’s left. Each elimination reduces remaining options. If you match two elements in one sector, you can cross reference other sectors to match.
Yeah, I need to see a demonstration of Irishman’s post. I’ll see what I can find on your link. (I was going to see if I could find a demonstration on YouTube, but haven’t gotten to it yet.)
As others have said, create an “elimination grid”. I used to do these puzzles all the time from those soft-cover pencil puzzle books, or from Games Magazine. Yes, there’s enough information; you don’t have to know what the last drink was. Doing a step-by-step would be a royal PITA (Pain-In-The-Ass) , but I got the following result grid (with no guessing):
House 1 - Yellow, Norwegian, Kools, Whiskey, Fox
House 2 - Blue, Ukrainian, Chesterfields, Tea, Horse
House 3 - Red, English, Old Gold, Milk, Snails
House 4 - White, Japanese, Parlaments, Orange Juice, Zebra
House 5 - Green, Spaniard, Lucky Strikes, Coffee, Dog
To prove how bad the step-by-step would be, if I were to do a step-by-step, I end up with…
There are five houses.
The Englishman lives in the red house.
The Spaniard owns the dog. (therefore the dog is not in the red house)
Coffee is drunk in the green house. (therefore the Englishman doesn’t drink coffee)
The Ukrainian drinks tea.(therefore the Ukranian doesn’t live in the red or green houses and doesn’t own the dog)
You can see where doing a step-by-step quickly gets bogged down.
1. Green is immediately right of White. After elimination, the last three houses are Red, Green, and White in some order. That means of those three houses, Red cannot be house 4, as that would separate Green and White.
I took too long to get this and now I can’t replicate my steps. But eventually I managed to get the crossrelations to eliminate out.
It’s not really a clue that was left out. It’s a question. The puzzle is a classic: Zebra Puzzle - Wikipedia
The full mystery is: “Now, who drinks water? Who owns the zebra?”
Also, if you want a completely customizable online grid to solve these things that can even automatically cross-reference your positive and negative results if you want, look here: Logical Solver – Johannes Singler's Private Website
As a bonus, it can auto-configure the Zebra puzzle for you, so you don’t have to manually enter the categories/options.
You also sometimes see one of these where you can’t solve everything, but where the question only asks one thing. Like with this one, since the question is who owns the zebra, it’s OK if you don’t know who lives in the red house.
) So after the first bit, I guessed.