How To Solve Einstein’s Riddle

Einstein’s Riddle is a logic grid puzzle allegedly created by Albert Einstein when he was a boy. It is said that only 2% of the population can solve it but I think we should have more faith in humanity, so let’s give it a whirl.

The Riddle

There are five differently coloured houses in a row. Each house is owned by someone of a different nationality who prefers a different beverage, smokes a different cigar and owns a different pet. You are kindly given 15 facts about these quite fussy people:

1. The Brit lives in the red house.
2. The Swede has a dog.
3. The Dane drinks tea.
4. The green house is next to the white house, on the left.
5. The owner of the green house drinks coffee.
6. The person who smokes Pall Mall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The owner of the centre house drinks milk.
9. The Norwegian lives in the first house.
10. The owner who smokes blends lives next to the one who has a cat.
11. The owner who has a horse lives next to the owner who smokes Dunhill.
12. The owner who smokes BlueMaster drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The owner who smokes blends has a neighbour who drinks water.

The question is, who owns the fish?

The Solution

So where do you even start with a puzzle like this? As the name ‘grid puzzle’ suggests, the best way to solve this kind of puzzle is to draw a grid with all the variables (house colour, nationality, preferred cigar, beverage and pet) and fill in the information you know; this helps you visualise all the clues. Here we go!

Start with the clues that give you information with a definite position. Clues 8 and 9 do this so we can use these first to tell us that the owner of house 3 drinks milk and that the Norwegian lives in house 1.

So that’s a nice and easy start. Now, here come the deductions! Let’s start with a simple one.

Clue 14 tells us that the Norwegian lives next to the blue house. However, the Norwegian lives at the end of the row, so the only house next to it is house 2. That means house 2 must be blue.

We know from clue 4 that the green house is directly on the left of the white house and we also know from clue 5 that the owner of the green house drinks coffee. This means that house 3 cannot be green as the owner drinks milk. So, for clue 4 to be satisfied, house 4 must be green and house 5 must be white.

Let’s fill all that in:

There are only 2 houses left that we don’t know the colour of: houses 1 and 3. Clue 1 tells us that the Brit lives in the red house. The Norwegian already lives in house 1 so the Brit must live in house 3; this means that house 3 is red.

From the other clues we know that the last colour left is yellow, therefore house 1 is yellow. Knowing this and using clue 7, we can just fill in that the owner of house 1 smokes Dunhill. Clue 11 tells us that the owner with a horse lives next to the owner who smokes Dunhill, who lives in house 1. The only house next to house 1 is house 2, therefore the owner with the horse lives there.

So now our grid looks like this:

Now we ask ourselves, of the remaining options – tea, water and beer -, what does the Norwegian drink? It can’t be tea, as Clue 3 tells us that’s the Dane; it can’t be beer as Clue 12 tells us that’s the drink of the owner who smokes BlueMaster, and the Norwegian smokes Dunhill; therefore, the Norwegian must drink water.

As you can see from the grid above, house 5 is the only house left that has neither a beverage nor a cigar filled in. So, from clue 12, house 5 must belong to the owner who smokes BlueMaster and drinks beer.

Clue 13 tells us that the German smokes Prince. The only house where we don’t yet know both the nationality and preferred cigar of the owner is house 4, therefore the German must live in the green house.

The last type of cigar is Pall Mall, so this must be smoked in house 3. Clue 6 tells us that the owner who smokes Pall Mall rears birds, so now we also know that there are birds in house 3.

Clue 10 states that the owner who smokes blends lives next to the one who owns cats. We know that the owner who smokes blends lives in house 2, so the cat owner must live in house 1 or 3. We already know that there are birds in house 3, so the cats must be in house 1.

The remaining animals, the dog and the fish, must be in houses 4 and 5. However, clue 2 tells us that the Swede has a dog. The German lives in house 4, so the Swede and the dog are in house 5.

This means that – drumroll, please – the German owns the fish!

And that’s Einstein’s Riddle solved!

I don’t know about you, but that little gap in house 2 is irksome so let’s fill it in just for completeness’ sake. We know that the Dane must live in house 2 and from clue 3 we know that the Dane drinks tea. Therefore, here is the completed grid:

So that’s how you solve Einstein’s Riddle. However, technically no clue mentions a fish. We just assumed it was the 5th pet, so you could sneakily say that the solution is that no one owns a fish, but where’s the fun in that?

Einstein’s puzzle is actually the ‘easier’ version of the Zebra Puzzle, in which you have one less clue and the green house is to the right of the white house. Surprisingly, these two small differences make the puzzle a lot more challenging.

This is the Zebra Puzzle, as seen in Life International in 1962:

• 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 ivory 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.

If you’re feeling brave, have a go at it!