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MathNet 2021 — Part 03 Question 89

Math Olympiad Vault · MathNet 2021 — Part 03

Question 89

Morgane and Bosphore play the following game. Morgane writes the integers $1$ through $8$ at the vertices of a regular octagon, one integer at each vertex. Bosphore then chooses a vertex and calculates the sum of the numbers at that vertex and its two neighbors. Calling this sum $s$, he gives Morgane $s$ candies.

Bosphore chooses a vertex so as to give Morgane as few candies as possible, while Morgane arranges the integers $1$ through $8$ so as to receive as many candies as possible. Prove that Bosphore will give her $12$ candies.