Twelve food units shared among four of ten kids
Question
A babysitter looks after hungry children and has identical units of food. She decides that exactly of the children will be fed and the other get nothing. In how many ways can she hand out all units so that each of the chosen children gets at least one unit?
Short answer
. Choose the four fed children in ways. Give each of them one unit first, then share the remaining units freely among the four, which by stars and bars can be done in ways. In total .
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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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