Rumour has it that Albert Einstein made up an impossibly difficult riddle when he was just a kid.
There’s no evidence to back up that apocryphal claim, but the rumour earned the popular logic puzzle the nickname “Einstein’s Riddle.”
Regardless of who actually came up with the riddle, it’s not terribly difficult to solve — if you have the patience to think it through. There are no tricks to this riddle. Like Sherlock Holmes, all you need is logic and deduction.
Here’s the riddle:
Five houses painted five different colours stand in a row. One person of a different nationality lives in each house. The five home owners all drink some type of beverage, smoke a certain cigar brand, and have a certain kind of pet. But none of the owners drink the same beverage, smoke the same type of cigar, or have the same pet.
And here are the clues:
1. The Brit lives in the red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the immediate left of the white house.
5. The green house’s owner drinks coffee.
6. The owner who smokes Pall Mall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The owner living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The owner who smokes Blends lives next to the one who keeps cats.
11. The owner who keeps the horse lives next to the one who smokes Dunhill.
12. The owner who smokes Bluemasters drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The owner who smokes Blends lives next to the one who drinks water.
The question is: Who owns the fish?
With so many variables (house number, house colour, nationality, drink, cigar, and pet), solving the puzzle gets complicated fast.
YouTube user PoETheeds did a great video walk through of how to solve the riddle, but here’s a quick run down.
The key to solving the riddle is to make a grid and start filling in what you know for sure about each house:
Start with the clues that you can immediately fill in on the grid. You know whoever lives in the center house drinks milk (clue number eight) and you know that the Norwegian lives in the first house (clue number nine).
Once you have those two squares filled in, you can use logic to fill in the rest. For example, clue 14 says the Norwegian lives next to the blue house. Since we already know the Norwegian lives in the first house, there’s only one house next to him. So house number two must be blue:
You can fill in much of the grid this way. Once you figure out who owns the horse though, things get tricky. At this point it’s helpful to label the rest of the empty boxes with all the remaining possibilities, and narrow it down from there.
Once you do that, you can see that water is the only possibility for house one. Then you can unravel the rest of the clues using the same deduction method as before.
Eventually you’ll fill in all the squares and figure out that (drum roll…) the German in house number four owns the fish.
To see the complete solution, watch PoETheeds’ full video walk through, below.
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