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Difficulty: 3/102025 IOQM 2025 (Q23)

In how many distinct ways can people be seated around a circular table? (Two seatings are considered identical if each person has the same left and right neighbors).

Options:

  • A.

    27

  • B.

    26

  • 24

  • D.

    25

Guide / Hint

Hint 1: In circular arrangements, absolute positions do not matter; only relative positions do. Fix the seat of 1 person first.

Hint 2: The number of ways to arrange items in a circle is .

Hint 3: Compute .

Solution

Step 1: For circular permutations of distinct objects, since there is no fixed starting position (the table can be rotated), we fix the position of one person to break the rotational symmetry.

Step 2: The remaining people can then be arranged in the remaining seats in linear order:

Step 3: For people, substitute :

So there are distinct circular seating arrangements.

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    2025 IOQM 2025 Q23 - Olympiad Math Olympiad Question | Leminno