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ASU 293 All Soviet Union MO 1980 1980 vectors in plane

Source:

July 19, 2019
vectorPlanecombinatorial geometrygeometry

Problem Statement

Given 19801980 vectors in the plane, and there are some non-collinear among them. The sum of every 19791979 vectors is collinear to the vector not included in that sum. Prove that the sum of all vectors equals to the zero vector.