The Einstein Riddle: A logic puzzle

A friend of mine posted this on their Facebook. I’d heard of it but never tried it out myself. FSo I figured, why not, and gave it a go. If you like logic puzzles, this is for you! This doesn’t have anything to do with Excel, other than that’s where I created the solution (file attached at the bottom of the post).

Originally this was called the Zebra Puzzle, but often called the Einstein Puzzle, was first published on December 17, 1962. The little I know about it, apparently it’s thought to be invented by Albert Einstein as a boy. It’s said that 98% of the world couldn’t solve it. I’m willing to bet it’s more like 90%. Maybe you can help prove me right, so post your results!

Einstein Portrait

Here is the puzzle. Below I’ll line out how I solved it, and the answer is in the attached Excel file. There are definitely some assumptions which need to be made and some things not to be taken too literally. This isn’t the original, and items have been changed out to make it more socially relevant, which I thought was a pretty cool twist.

ASSUMPTIONS

  • There are 5 separate houses
  • Each house is a different color
  • One person of each nationality lives alone in a separate house
  • Each person drinks a specific beverage
  • Each person uses a specific console
  • Each person uses a specific phone
  • Each item is unique and can’t be used twice by any other person
  • Each person is a man (sorry ladies, it’s just how the hints are laid out)

There is a clue which describes left vs. right for the houses. Just imagine the houses on a street and you’re looking at them, left to right. Don’t get too technical with this part. They’re just houses next to each other.

THE PUZZLE

Question: Who has the iPhone 5s?

HINTS

  1. The Brit lives in a Blue house
  2. The French owns a Galaxy S5
  3. The German drinks Coca Cola
  4. The Red house is next to, and on the left of, the White house
  5. The owner of the Red house drinks Coffee
  6. The person who plays on the PC owns an MSLumia
  7. The owner of the Green house plays on an Xbox One
  8. The man living in the center house drinks Water
  9. The American lives in the first house
  10. The man who plays on a PS4 lives next to the one who owns an iPhone 6
  11. The man who owns a Galaxy S6 lives next to the man who plays on an Xbox One
  12. The man who plays on a PS3 drinks beer
  13. The Swedish plays on an Xbox 360
  14. The American lives next to the Yellow house
  15. The man who plays on a PS4 has a neighbor who drinks Pepsi

That’s it! Go forth and conquer. Yes there is an answer, and yes you can get it from only these clues and rules. But no, it’s not easy. 🙂 What was your answers?

SOLUTION

SPOILERS BELOW THIS POINT!!

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DO NOT SCROLL DOWN UNLESS YOU WANT TO SEE THE ANSWERS!!

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Hints 10, 11, and 15, are the only hints which give us neighboring facts. The others give us known constants. So we have 12 known item combinations, and we only need to find their locations within the group.

Here is what we know:

  • the American is in the first house, who neighbors a Yellow house,
  • the middle house drinks Water,
  • the German drinks Coke,
  • the French has a Galaxy 5S,
  • the Red house has Coffee and is left of the White house,
  • the house with the PC owns an MSLumia,
  • the Green house has an Xbox One,
  • the house with the PS3 has Beer,
  • and the Swedish has an Xbox 360.

Step 1

This gives us the information seen below, which we can assign possible rows, or house numbers, to each known fact. In the sample file I’ve done this in column B.

The easy way to go about this is much like a Sudoku puzzle. Find only the items which can belong in a certain row. Note I went with the houses going down rows, but this can be accomplished going across columns just the same (i.e. transposed).

Einstein Riddle - Solution1

Step 2

Since we know the Red and White houses go together, and whoever is in the Red house drinks Coffee, we know those can’t be in row 1 (as listed in the above image) since they go together, which means they can only live in rows 4 and 5 respectively. We can then move those facts to the top table of known item locations. We can then update the remaining facts with their now possible locations based on the updated table of known item locations, as seen in the below image.

Einstein Riddle - Solution2

Step 3

We know the Brit lives in a Blue house, which now only has one logical place it could be, which is number 3. When we put in that information we can then see the only house color remaining is Green, which means that’s the American’s house color. Also, since the Green house has the Xbox One, we can fill that in too. The updated information should now look like the below image.

Einstein Riddle - Solution3

 

(Note for the above image, the PC and MSLumia possible combinations should exclude row 1 at this point in lieu of the Xbox One in the Green house.)

Step 4

Since we know the man who owns a Galaxy S6 lives next to the man who plays on an Xbox One, from hint #11, and we know the American has the Xbox One, we can safely assume the second house (which is Yellow) has the Galaxy S6.

Additionally, we know the person with the PS4 has one neighbor with an iPhone 6, and another neighbor who drinks Pepsi. This leaves a few possibilities. But since we know that whomever has the PS3 drinks Beer, and can go into rows 2 or 5, and also that the PS4 possibilities can only be in rows 2 or 4, and not 5, then Beer and PS3 can’t go into 2 so it must go in 5.

Einstein Riddle - Solution4

Step 5

Here is where things start to go fast! There are several steps back-to-back here, so if you’re trying to follow along, read carefully!

There are still two possibilities for where the iPhone 6 could be. Let’s just table that for now. Instead, we have only one possibility for the Swedish and Xbox 360, which can only fit in row 4.

After this goes in we know the German who drinks Coke can only fit in row 2.

And once we have those two items in, we know the French with the Galaxy 5S can only go into row 5.

Finally, since we know the PC owner has an MSLumia, that can only fit in row 3 now.

Going back to our iPhone 6, we now have one possibility, row 1.

By this point there should only be one open space – for the iPhone 5s!

We should be able to deduce that the Swedish man lived in the 4th house, which is Red, he drinks Coffee, plays on an Xbox 360, and unfortunately has an iPhone 5s.

Einstein Riddle - Solution Final

I had a lot of fun figuring this out.

Solution file: Einstein Riddle

2 thoughts on “The Einstein Riddle: A logic puzzle

  1. These logic puzzles are great. My wife has books of them that she doles out to her 8th grade math classes. She says the best students just eat them up, while the typical student spends two minutes, then gives up.

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