Testing LLM Reasoning: A Solar Eclipse Probability Math Problem

Afinetheorem · x · 2026-08-10

The author poses a Fermi-style math problem about solar eclipse probability to serve as an 'elegance test' for LLMs.

The author's simple paper solution estimates an average path width of 100 miles, calculating that one would experience a total eclipse within 200 miles of their location during an 80-year lifetime.

Testing reveals that many LLMs resort to complex calculations starting from Earth's surface area, while some newer models (like GPT 5.6) manage to find the simpler, precise method. The author suggests this would make for a great benchmark.

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