### [Four mathematicians who have collaborated in pairs – an introductory problem on the principle of inclusion and exclusion](https://www.thinkhow.tech/en/article/747)

**Published:** 2026-07-26T06:40:28

**Author:** thinker007

**Excerpt:** 344}}

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**Tags:** 中级_en, 交互_en, 奥数_en, 知识_en

**Categories:** 学科_en, 数学_en

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