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MathNet 2018-part-02 — 181 problems (EN–VI) Question 164

Math Olympiad Vault · MathNet 2018-part-02 — 181 problems (EN–VI)

Question 164

Find all integers $n \geqslant 3$ such that, if $a_{1}, \ldots, a_{n}$ are strictly positive reals such that $\max \left(a_{1}, \ldots, a_{n}\right) \leqslant n \cdot \min \left(a_{1}, \ldots, a_{n}\right)$, then there necessarily exist three of these reals that are the side lengths of an acute triangle, that is, a triangle whose three angles are all strictly acute.