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Homothetic Triangles

Source: Iran 3rd round 2009 - final exam problem 3

January 2, 2015
ratiogeometrygeometric transformationhomothetygeometry unsolved

Problem Statement

An arbitary triangle is partitioned to some triangles homothetic with itself. The ratio of homothety of the triangles can be positive or negative. Prove that sum of all homothety ratios equals to 11.
Time allowed for this problem was 45 minutes.