Short Probability (permutation) question

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SUMMARY

The problem involves calculating the number of seating arrangements for 19 students in a semi-circle, with the condition that 4 specific students must sit next to each other. The correct approach is to treat the 4 students as a single unit, resulting in 16 units to arrange. Therefore, the total arrangements are calculated as 15! x 4!, where 15! accounts for the arrangement of the 16 units and 4! accounts for the internal arrangement of the 4 students.

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  • Understanding of factorial notation and its application in permutations
  • Basic knowledge of combinatorial principles
  • Familiarity with seating arrangements in circular permutations
  • Concept of treating groups as single units in permutations
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  • Study circular permutations and their unique properties
  • Learn about advanced combinatorial techniques in probability
  • Explore examples of grouping in permutations
  • Review factorial calculations and their applications in probability problems
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jasper10
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Homework Statement



There is a total of 19 students sitting in a semi-cirlce. How many seating arrangements are possible, if 4 of the 19 students have to sit next to each other?


The Attempt at a Solution



I'm not sure if the calculation is:

15! x 4!

or

19! / 4!

Thanks!
 
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jasper10 said:

Homework Statement



There is a total of 19 students sitting in a semi-cirlce. How many seating arrangements are possible, if 4 of the 19 students have to sit next to each other?


The Attempt at a Solution



I'm not sure if the calculation is:

15! x 4!

or

19! / 4!

Thanks!

I would go with the first answer, assuming you can explain it. :smile:
 

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