IPMAT/Modern Math•1yr
solulu

Circular Permutation

I got this explanation but can't we make them both sit first and then do 15!-13!

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Comments (2)

S
solulu
OP•1yr

Oh okay thank you

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V
vani.agr
IIM Indore
MOD•1yr

Your thought about 15!−13! seems natural, but that would apply to linear arrangements (a row), not circular ones. If you fix two people first and subtract “bad” cases, you must be careful with circular permutations — because seating in a circle is not the same as line permutations. Fixing both at once risks double counting rotations or misplacing the circular symmetry.

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