Maths Olympiad Prep

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, 2026

Combinatorics Difficulty 5.0 AIME, harder Find the answer United Kingdom

Deindra wants to arrange the five numbers 1, 2, 3, 4, and 5 into a row such that the last number is odd, and the sum of any three adjacent numbers is divisible by the first number of the three. How many such arrangements could she make?

(A) 11 (B) 22 (C) 33 (D) 44 (E) 55

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