Einstein’s Riddle, also known as the Zebra Puzzle, is a classic logic puzzle that challenges your deductive reasoning skills. In this blog post, using x.AI’s GROK, we’ll tackle the puzzle step by step to answer the question: Who owns the fish? We’ll break down the clues, build a solution systematically, and present the final answer in a clear, engaging way, as if explaining it to a curious reader.
Abdalla Harem | September 9, 2025 | 6 min read
The Main logic puzzle: There are 5 houses in a row, each with a different color: yellow, blue, red, green, and white. In each house lives a person of a different nationality: Norwegian, Dane, Brit, German, and Swede. Each drinks a different beverage: water, tea, milk, beer, and coffee. Each smokes a different brand: Dunhill, blends, Pall Mall, BlueMaster, and Prince. Each has a different pet: cats, horses, birds, fish, and dogs. The clues are: The Brit lives in the red house. The Swede keeps dogs as pets. The Dane drinks tea.
The greenhouse is on the left of the white house. The greenhouse’s owner drinks coffee. The person who smokes Pall Mall rears birds. The owner of the yellow house smokes Dunhill. The man living in the center house drinks milk. The Norwegian lives in the first house. The man who smokes lives next to the one who keeps cats. The man who keeps horses lives next to the man who smokes Dunhill. The owner who smokes BlueMaster drinks beer. The German smokes Prince. The Norwegian lives next to the blue house. The man who smokes blends has a neighbor who drinks water. Who owns the fish? Explain step-by-step with xAI’s Grok.
The Puzzle – Einstein’s Riddle: Who Owns the Fish?
Imagine five houses in a row, numbered 1 to 5 from left to right. Each house has a unique:
- Color: yellow, blue, red, green, white
- Nationality: Norwegian, Dane, Brit, German, Swede
- Drink: water, tea, milk, beer, coffee
- Smoke: Dunhill, blends, Pall Mall, BlueMaster, Prince
- Pet: cats, horses, birds, fish, dogs
The goal is to determine who owns the fish using the following 15 clues:
- The Brit lives in the red house.
- The Swede keeps dogs as pets.
- The Dane drinks tea.
- The greenhouse is on the left of the white house.
- The greenhouse’s owner drinks coffee.
- The person who smokes Pall Mall rears birds.
- The owner of the yellow house smokes Dunhill.
- The man living in the center house drinks milk.
- The Norwegian lives in the first house.
- The man who smokes blends lives next to the one who keeps cats.
- The man who keeps horses lives next to the man who smokes Dunhill.
- The owner who smokes BlueMaster drinks beer.
- The German smokes Prince.
- The Norwegian lives next to the blue house.
- The man who smokes blends has a neighbor who drinks water.
Let’s dive in and solve it step by step, as if we’re unraveling a mystery together!
Step-by-Step Solution
To solve this, we’ll assign attributes to each house, using a table to track our progress. We’ll apply each clue logically, eliminating impossibilities until we find the fish’s owner. Think of it like a detective’s caseboard, piecing together evidence.
Step 1: Setting Up the Board
We have five houses (1 to 5), and each attribute (nationality, color, drink, smoke, pet) is unique per house. We’ll start with an empty table:
| House | Nationality | Color | Drink | Smoke | Pet |
|---|---|---|---|---|---|
| 1 | ? | ? | ? | ? | ? |
| 2 | ? | ? | ? | ? | ? |
| 3 | ? | ? | ? | ? | ? |
| 4 | ? | ? | ? | ? | ? |
| 5 | ? | ? | ? | ? | ? |
Step 2: Applying the First Clues
Let’s start with clues that give us direct assignments.
- Clue 9: The Norwegian lives in the first house.
- House 1: Nationality = Norwegian.
- Clue 8: The man living in the center house drinks milk.
- Center house is House 3: Drink = milk.
- Clue 14: The Norwegian lives next to the blue house.
- Norwegian is in House 1, so the blue house must be next to it, in House 2.
- House 2: Color = blue.
Our table now looks like this:
| House | Nationality | Color | Drink | Smoke | Pet |
|---|---|---|---|---|---|
| 1 | Norwegian | ? | ? | ? | ? |
| 2 | ? | blue | ? | ? | ? |
| 3 | ? | ? | milk | ? | ? |
| 4 | ? | ? | ? | ? | ? |
| 5 | ? | ? | ? | ? | ? |
Step 3: Colors and the Greenhouse
- Clue 4: The greenhouse is on the left of the white house.
- This means green and white houses are adjacent, with green to the left: possible pairs are 1-2, 2-3, 3-4, or 4-5.
- But House 2 is blue, so it can’t be green or white. This eliminates 1-2 and 2-3.
- Possible pairs: 3-4 (green-white) or 4-5 (green-white).
- Clue 5: The greenhouse’s owner drinks coffee.
- The greenhouse has coffee as its drink.
- House 3 has milk, so it can’t be green (or have coffee). This eliminates the 3-4 pair.
- Therefore, green must be House 4, and white must be House 5.
- House 4: Color = green, Drink = coffee.
- House 5: Color = white.
- Clue 1: The Brit lives in the red house.
- The remaining colors for Houses 1 and 3 are yellow and red.
- Let’s test: if House 3 is yellow, then House 1 is red (only colors left).
- But red = Brit (Clue 1), so House 1 would be Brit. This contradicts Clue 9 (House 1 is Norwegian).
- Therefore, House 1 must be yellow, and House 3 must be red.
- House 3: Color = red, Nationality = Brit (since Brit lives in red).
- Clue 7: The owner of the yellow house smokes Dunhill.
- House 1 is yellow, so Smoke = Dunhill.
Updated table:
| House | Nationality | Color | Drink | Smoke | Pet |
|---|---|---|---|---|---|
| 1 | Norwegian | yellow | ? | Dunhill | ? |
| 2 | ? | blue | ? | ? | ? |
| 3 | Brit | red | milk | ? | ? |
| 4 | ? | green | coffee | ? | ? |
| 5 | ? | white | ? | ? | ? |
Step 4: Placing Pets
- Clue 11: The man who keeps horses lives next to the man who smokes Dunhill.
- Dunhill is in House 1, so horses must be in House 2 (the only neighbor).
- House 2: Pet = horses.
- Clue 6: The person who smokes Pall Mall rears birds.
- Pall Mall smoker has birds.
- Clue 10: The man who smokes blends lives next to the one who keeps cats.
- Blends Smoker is next to the cat’s owner.
- Clue 2: The Swede keeps dogs as pets.
- Swede has dogs.
Updated table:
| House | Nationality | Color | Drink | Smoke | Pet |
|---|---|---|---|---|---|
| 1 | Norwegian | yellow | ? | Dunhill | ? |
| 2 | ? | blue | ? | ? | horses |
| 3 | Brit | red | milk | ? | ? |
| 4 | ? | green | coffee | ? | ? |
| 5 | ? | white | ? | ? | ? |
Step 5: Drinks and Nationalities
- Clue 3: The Dane drinks tea.
- Dane has tea. Remaining drinks for Houses 1, 2, 5: water, tea, beer.
- Clue 12: The owner who smokes BlueMaster drinks beer.
- BlueMaster smoker has beer.
- Clue 15: The man who smokes blends has a neighbor who drinks water.
- Blends smoker has a neighbor with water.
- Clue 13: The German smokes Prince.
- German has Prince.
Remaining nationalities for Houses 2, 4, 5: Dane, German, Swedish.
Let’s try placing the Brit’s smoke in House 3. Possible smokes: blends, Pall Mall, BlueMaster, Prince.
- BlueMaster = beer, but House 3 has milk (not beer).
- Prince = German, but House 3 is Brit (not German).
- So, House 3 smoke: blends or Pall Mall.
Case: House 3 smokes Pall Mall.
- Then, House 3: Pet = birds (Clue 6).
- Remaining smokes for 2, 4, 5: blends, BlueMaster, Prince.
- Remaining pets for 1, 4, 5: cats, fish, dogs (since 2 has horses, 3 has birds).
- Blends next to cats (Clue 10).
- Blends in 2, 4, or 5.
- If blends in 2: neighbors 1 and 3, so cats in 1 (since 3 is birds).
- If blends in 4: neighbors 3 and 5, so cats in 5 (since 3 is birds).
- If blends in 5: neighbor 4, so cats in 4.
Now, water neighbor to blends (Clue 15). Possible water houses: 1, 2, 5.
- BlueMaster = beer, so beer in 2 or 5 (since 1 has water or tea, but let’s see).
- If BlueMaster in 2: beer in 2.
- If BlueMaster in 5: beer in 5.
Remaining smokes: 2, 4, 5: blends, BlueMaster, Prince.
Try water placement with blends:
- Water in 1, 2, or 5.
- Dane = tea, in 2 or 5 (since 4 has coffee, 3 milk, 1 Norwegian ≠ Dane).
Try Dane in 2: tea in 2.
- Then House 5: Swede (dogs, Clue 2).
- Drinks left: 1 and 5: water, beer.
- BlueMaster = beer, in 2 or 5.
- If BlueMaster in 5: beer in 5, water in 1.
- Blends need water, neighbor.
- If blends in 2: neighbor 1 (water), yes!
- So: House 2: blends.
- Remaining smokes for 4 and 5: BlueMaster, Prince.
- BlueMaster in 5 (since 2 is blends), so House 5: BlueMaster, beer.
- House 4: Prince, so German (Clue 13).
- House 1: water.
Now, pets: 2 horses, 3 birds, 5 dogs.
- Remaining pets: cats, fish for 1, 4.
- Blends (2) next to cats: neighbors 1 and 3. Since 3 is birds, cats in 1.
- House 1: cats.
- House 4: fish.
Final table:
| House | Nationality | Color | Drink | Smoke | Pet |
|---|---|---|---|---|---|
| 1 | Norwegian | yellow | water | Dunhill | cats |
| 2 | Dane | blue | tea | blends | horses |
| 3 | Brit | red | milk | Pall Mall | birds |
| 4 | German | green | coffee | Prince | fish |
| 5 | Swede | white | beer | BlueMaster | dogs |
Verification
Let’s check all clues:
- Clue 1: Brit in red house: House 3, yes.
- Clue 2: Swede keeps dogs: House 5, yes.
- Clue 3: Dane drinks tea: House 2, yes.
- Clue 4: Green left of white: House 4 green, House 5 white, yes.
- Clue 5: Greenhouse drinks coffee: House 4, yes.
- Clue 6: Pall Mall rears birds: House 3, yes.
- Clue 7: Yellow house smokes Dunhill: House 1, yes.
- Clue 8: Center house drinks milk: House 3, yes.
- Clue 9: Norwegian in first house: House 1, yes.
- Clue 10: Blends next to cats: House 2 (blends) next to House 1 (cats), yes.
- Clue 11: Horses next to Dunhill: House 2 (horses) next to House 1 (Dunhill), yes.
- Clue 12: BlueMaster drinks beer: House 5, yes.
- Clue 13: German smokes Prince: House 4, yes.
- Clue 14: Norwegian next to blue: House 1 next to House 2 (blue), yes.
- Clue 15: Blends has a neighbor who drinks water: House 2 (blends) next to House 1 (water), yes.
Everything checks out!
The Answer
Who owns the fish? The fish is owned by the German, who lives in House 4.
This puzzle is a fantastic brain teaser, requiring careful deduction and patience. By systematically applying each clue, we narrowed down the possibilities and found the solution. Try solving it yourself or share it with friends to see who can crack it first!
We tried to solve this via x.Ai’s Grok. It might be interesting to try a different model. Would you like to try? Or suggest a method below, and we will dive into it.
