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A Slice of Bad Luck

Дата публикации: 13-10-2026 15:51:44



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  • Level: High School 
  • Thread starter Thread starter bob012345
  • Start date Start date Oct 8, 2026
bob012345
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... how many slices does each person want (24 slices and 9 people, if they want 3 each the probability is again 1)?
... many other missing constraints

@bob012345 you need to think more about what constraints are needed to give this problem a meaningful solution.

bob012345
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... how many slices does each person want (24 slices and 9 people, if they want 3 each the probability is again 1)?
... many other missing constraints

@bob012345 you need to think more about what constraints are needed to give this problem a meaningful solution.


This is a real life problem. The party is tomorrow. In my OP I stated that there are 12 slices of 6 varieties on each platter. That is two slices of each kind per platter. There are two platters because each platter only holds 12 slices and I wanted more for the party. That’s just how they are sold.

In order to approach such a problem one has to make some assumptions. I think it’s reasonable to assume each variety is equally desired by people.

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Hornbein
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I think it’s reasonable to assume each variety is equally desired by people.
Then everyone gets something they like.
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That's fine. But if you ask a physics forum for a numerical answer, you should state those assumptions.
In the real world, you give them the 2 platters and tell anyone who complains to shut up. ;-)

At least that is what I would do, but I have very few friends. ;-)

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You have four slices of one kind. Cut one slice to equal three pieces. Now you have 12 pieces > 9 people.

Another approach
3 people have 2 cakes. 6 people have 3 cakes.
Let the three, say a b c, choose their favorite by two turns, ordered abc cba.
Then let the six, say d e f g h i, choose by two turns ordered defghi ihgfed. The six draw lot for the final turn order.
Someone gourmet but less appetite may want to belong to the three.

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Experimental solution
  1. Call each person and ask them what kind of cheesecake and how many pieces they want.
  2. Order appropriately.
  3. The probability that someone will not get what they want is zero.
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Experimental solution
  1. Call each person and ask them what kind of cheesecake and how many pieces they want.
  2. Order appropriately.
  3. The probability that someone will not get what they want is zero.
I could buy just one platter and call each person offering them a choice among the available varieties. The first person can choose among the six…assorted possibilities happen…for the ninth person there are four slices left so they still have a choice. The last person has a choice which could be from two to four but doesn't know the first person had a choice of six. Everyone is satisfied and I only had to buy one platter!
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Here is what I got.
Well it turns out that there is about a 5.37% chance that someone will be unhappy and not get what they want. If I buy only one platter of cheesecake, that raises to an 84.25% chance someone will be unhappy. This is exactly the birthday problem using 6 for the number of days of the year which represents preference and using 5 for the number of people with the same preference. That’s because there are only four slices of a given kind so with 5 people preferring that someone is unhappy. For a case of only one platter, that number is 3 since only two slices of a given kind are available.

The exact numbers are ##\frac{22549}{419904} ≈0.0537## and ##\frac{6551}{7776} ≈0.8425##

[\Spoiler]

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It turned out that only 7 of the 9 people came and I bought only one cheesecake platter, which had twelve slices, two of each kind. That computed to a 54% chance at least someone would be unhappy. There were at least 5 slices left over so maybe that’s why? Here is a good site with a birthday problem calculator;

https://www.dcode.fr/birthday-problem

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sbrothy
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I hate cheesecake. Count me out. :smile:

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