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MathNet 2017-part-06 — 176 problems (EN–VI) Question 93

Math Olympiad Vault · MathNet 2017-part-06 — 176 problems (EN–VI)

Question 93

Determine the smallest real constant $C$ such that for all $a_{1}, a_{2}, a_{3}, a_{4}, a_{5} \in \mathbb{R}_{\gt 0}$, not necessarily distinct, there always exist four distinct indices $i, j, k, l$ such that:
$$
\left|\frac{a_{i}}{a_{j}}-\frac{a_{k}}{a_{l}}\right| \leq C
$$