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MathNet 2021 — Part 04 Question 65

Math Olympiad Vault · MathNet 2021 — Part 04

Question 65

Alice and Bob play a game on the plane. Firstly, Alice draws 4 red points which are the vertices of a square, and draws another 2021 red points inside this square such that no three red points are collinear. Next, Bob draws $n$ blue points such that for every triangle whose three vertices are the red points, there is at least one blue point lying strictly inside this triangle.

The goal of Alice is to maximize $n$, while the goal of Bob is to minimize $n$. Find the value of $n$ if both players play optimally.