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Romania District MO 2022 Grade 9 P4

Source: Romania District MO 2022 Grade 9

March 28, 2022
romaniageometryvector

Problem Statement

We call a set of 66 points in the plane splittable if we if can denote its elements by A,B,C,D,EA,B,C,D,E and FF in such a way that ABC\triangle ABC and DEF\triangle DEF have the same centroid.
[*]Construct a splittable set. [*]Show that any set of 77 points has a subset of 66 points which is not splittable.