Can you solve “Einstein’s Riddle”?

Before he turned physics upside down, a young Albert Einstein supposedly showed off his genius by devising a complex riddle involving this list of clues. Can you resist tackling a brain teaser written by one of the smartest people in history? Let’s give it a shot. The world’s rarest fish has been stolen from the city aquarium. The police have followed the scent to a street with five identical looking houses. But they can’t search all the houses at once, and if they pick the wrong one, the thief will know they’re on his trail. It’s up to you, the city’s best detective, to solve the case. When you arrive on the scene, the police tell you what they know.

One: each house’s owner is of a different nationality, drinks a different beverage, and smokes a different type of cigar. Two: each house’s interior walls are painted a different color. Three: each house contains a different animal, one of which is the fish. After a few hours of expert sleuthing, you gather some clues. It may look like a lot of information, but there’s a clear logical path to the solution. Solving the puzzle will be a lot like Sudoku, so you may find it helpful to organize your information in a grid, like this. Pause the video on the following screen to examine your clues and solve the riddle.

Answer in: 3 2 1 To start, you fill in the information from clues eight and nine. Immediately, you also realize that since the Norwegian is at the end of the street, there’s only one house next to him, which must be the one with the blue walls in clue fourteen. Clue five says the green-walled house’s owner drinks coffee. It can’t be the center house since you already know its owner drinks milk, but it also can’t be the second house, which you know has blue walls. And since clue four says the green-walled house must be directly to the left of the white-walled one, it can’t be the first or fifth house either.

The only place left for the green-walled house with the coffee drinker is the fourth spot, meaning the white-walled house is the fifth. Clue one gives you a nationality and a color. Since the only column missing both these values is the center one, this must be the Brit’s red-walled home. Now that the only unassigned wall color is yellow, this must be applied to the first house, where clue seven says the Dunhill smoker lives. And clue eleven tells you that the owner of the horse is next door, which can only be the second house. The next step is to figure out what the Norwegian in the first house drinks. It can’t be tea, clue three tells you that’s the Dane.

As per clue twelve, it can’t be root beer since that person smokes Bluemaster, and since you already assigned milk and coffee, it must be water. >From clue fifteen, you know that the Norwegian’s neighbor, who can only be in the second house, smokes Blends. Now that the only spot in the grid without a cigar and a drink is in the fifth column, that must be the home of the person in clue twelve. And since this leaves only the second house without a drink, the tea-drinking Dane must live there.

The fourth house is now the only one missing a nationality and a cigar brand, so the Prince-smoking German from clue thirteen must live there. Through elimination, you can conclude that the Brit smokes Pall Mall and the Swede lives in the fifth house, while clue six and clue two tell you that these two have a bird and a dog, respectively. Clue ten tells you that the cat owner lives next to the Blend-smoking Dane, putting him in the first house. Now with only one spot left on the grid, you know that the German in the green-walled house must be the culprit. You and the police burst into the house, catching the thief fish-handed.

While that explanation was straightforward, solving puzzles like this often involves false starts and dead ends. Part of the trick is to use the process of elimination and lots of trial and error to hone in on the right pieces, and the more logic puzzles you solve, the better your intuition will be for when and where there’s enough information to make your deductions. And did young Einstein really write this puzzle? Probably not. There’s no evidence he did, and some of the brands mentioned are too recent. But the logic here is not so different from what you’d use to solve equations with multiple variables, even those describing the nature of the universe.

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