ISL 2020 C2
In a regular 100-gon, 41 vertices are colored black and the remaining 59 vertices are colored white. Prove that there exist 24 convex quadrilaterals whose corners are vertices of the 100 -gon, so that - the quadrilaterals are pairwise disjoint, and - every quadrilateral has three corners of one color and one corner of the other color. (Austria)
Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.
Official text: IMO 2020 Shortlist booklet, page 8.
Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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