1. The Emperor
You are the ruler of a medieval empire and you are about to have a celebration tomorrow. The celebration is the most important party you have ever hosted. You've got 1000 bottles of wine you were planning to open for the celebration, but you find out that one of them is poisoned.
The poison exhibits no symptoms until death. Death occurs within ten to twenty hours after consuming even the minutest amount of poison.
You have over a thousand slaves at your disposal and just under 24 hours to determine which single bottle is poisoned.
You have a handful of prisoners about to be executed, and it would mar your celebration to have anyone else killed.
What is the smallest number of prisoners you must have to drink from the bottles to be absolutely sure to find the poisoned bottle within 24 hours?
Added 1 January 2007 · Updated 2 July 2026
Hint: It is much smaller than you first might think. Try to solve the problem first with one poisoned bottle out of eight total bottles of wine.
Solution:
10 prisoners must sample the wine. Bonus points if you worked out a way to ensure than no more than 8 prisoners die.
Number all bottles using binary digits. Assign each prisoner to one of the binary flags. Prisoners must take a sip from each bottle where their binary flag is set.
Here is how you would find one poisoned bottle out of eight total bottles of wine.
| |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| Prisoner A |
|
X |
|
X |
|
X |
|
X |
| Prisoner B |
|
|
X |
X |
|
|
X |
X |
| Prisoner C |
|
|
|
|
X |
X |
X |
X |
In the above example, if all prisoners die, bottle 8 is bad. If none die, bottle 1 is bad. If A & B dies, bottle 4 is bad.
With ten people there are 1024 unique combinations so you could test up to 1024 bottles of wine.
Each of the ten prisoners will take a small sip from about 500 bottles. Each sip should take no longer than 15 seconds and should be a very small amount. Small sips not only leave more wine for guests. Small sips also avoid death by alcohol poisoning. As long as each prisoner is administered about a millilitre from each bottle, they will only consume the equivalent of about one bottle of wine each.
Each prisoner will have at least a fifty percent chance of living. There is only one binary combination where all prisoners must sip from the wine. If there are ten prisoners then there are ten more combinations where all but one prisoner must sip from the wine. By avoiding these two types of combinations you can ensure no more than 8 prisoners die.
One viewer felt that this solution was in flagrant contempt of restaurant etiquette. The emperor paid for this wine, so there should be no need to prove to the guests that wine is the same as the label. I am not even sure if ancient wine even came with labels affixed. However, it is true that after leaving the wine open for a day, that this medieval wine will taste more like vinegar than it ever did. C'est la vie.
Comments (28)
Um, maybe I'm missing something, but on The Emperor, if two prisoners take drinks from the same bottle in multiple places, you can't tell which bottle is poisoned. You can only narrow it down to two.
In 'The Emperor', if two prisoners take drinks from the same bottle in multiple places, you can't tell which bottle is poisoned. You can only narrow it down to two.
Your solution to The Emperor puzzle suggests a different approach to minimize casualties, which is interesting. However, the original riddle's wording may lead to different interpretations.
The answer for "the emperor" question can be 2.
Please provide the answer for 'The Emperor' question. I am really desperate to find the solution.
Please provide the answer for 'The Emperor'.
I am desperate to find the solution for 'The Emperor'. I think there is no answer provided, which is frustrating.
The solution to The Emperor is not showing. I got it right with 10 but am not sure exactly how I came to this result. Can I see the workings out please?
The Emperor (and the poisoned wine bottle) is a great puzzle. It made me feel for the first time that binary digits can be fun!
The bottles can be divided into three groups of 333 bottles each, with one extra bottle. We need to make one glass of wine from each group by mixing a minute amount from each bottle from the respective group to identify which group has the poisoned bottle.
The bottles can be divided into three groups consisting of 333 bottles each, with one extra bottle. We need to make one glass of wine from each group by mixing a minute amount from each bottle from the respective group to identify the poisoned bottle.
The solution to 'The Emperor' is not present on the site.
If a prisoner will drink from 500 bottles, and it takes around 30 seconds to drink from each bottle, it will take him 250 minutes, which is slightly more than 4 hours. Then the emperor must wait 20 hours, so the party will start late.
If we number the bottles in ternary digits and take out the 2 combinations with no zeros, the 448 combinations with 1 zero, and the 672 combinations with 2 zeros, we still have 1065 combinations to play with, in which only a maximum of 4 slaves will die. We would need 14 slaves for this method.
The method of using ternary digits to number the bottles in 'The Emperor' puzzle is interesting. However, the maximum death toll of 1 slave is indeed the safest approach, as you mentioned.
Just wondering, how would they know which of the bottles the prisoners sipped from is the poison? Each prisoner had to test "about 500 bottles"; how do they conclude which one caused death?
The timing of the poison's effects raises questions. If death occurs 10 to 20 hours after consumption, how can the prisoners determine which bottle caused the death within the 24-hour timeframe? The symptoms don't appear until after 10 hours, complicating their conclusions.
The answer to "The Emperor" puzzle is that only 4 prisoners die. The first 1000 bottles are divided into 10 sets of 100 bottles, and each glass is filled a little from all 100 bottles.
We have 24 hours. In a maximum of 12 hours, we can get results. We can repeat the procedure for 2 trials, thus needing a minimum of 9 prisoners to give us 512 unique combinations. This way, only a maximum of 8 people may die.
The answer for 'The Emperor' question can be 2.
In the puzzle and the answer to #1 "The Emperor", you say that death occurs after consuming even the minutest amount of poison and that you have under 24 hours to determine which single bottle is poisoned.
The solution for 'The Emperor' involves using 9 prisoners to test 500 bottles, allowing for unique combinations and minimizing deaths.
The answer to the question "the emperor" is that only one prisoner can taste a single drop from every bottle. The bottle from which he dies is the poisoned one.
For 'The Emperor', only one prisoner can taste from each bottle, and the poisoned one is identified by the one who dies.
Could you please send across the solution to 'The Emperor' puzzle as it is not present on the site?
In the emperor and 1000 wine bottles, I have a solution. At time zero, the guards mix 1ml wine from 250 of the bottles into 1 glass, 1 ml from the 2nd set of 250 bottles into a second glass and so on into third and fourth glasses.
If a prisoner drinks from 500 bottles, it will take him 250 minutes, which is slightly more than 4 hours. Then the emperor must wait 20 hours, so the party will start late.
The expression "You have a handful of prisoners about to be executed" has misled me into believing you only have 5 prisoners to be executed, which can make it even harder. I would suggest changing to "(...)a limited amount of prisoners(...)".
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