Splitting white and black balls into bowls of three
Question
There are identical white balls and identical black balls, and distinguishable bowls. In how many ways can all the balls be placed so that every bowl ends up with exactly balls?
Short answer
. Once each bowl's number of white balls is set, black balls fill the rest uniquely, so count with . Stars and bars gives ; subtract the solutions where some bowl has at least 4 (two such bowls is impossible), leaving .
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Open the worked solutionLessons behind this question
- Counting and Combinatorics
- Sample Spaces, Events, and the Probability Axioms
- Conditional Probability, Total Probability, and Bayes' Rule
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