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a convex hexagon "inscribed" in a polygon with area 3/4

Source: mock tst romania 2004

December 31, 2004
geometryareapolygonconvex polygongeometric inequalityIMO Shortlist

Problem Statement

Let PP be a convex polygon. Prove that there exists a convex hexagon that is contained in PP and whose area is at least 34\frac34 of the area of the polygon PP.
Alternative version. Let PP be a convex polygon with n6n\geq 6 vertices. Prove that there exists a convex hexagon with
a) vertices on the sides of the polygon (or) b) vertices among the vertices of the polygon
such that the area of the hexagon is at least 34\frac{3}{4} of the area of the polygon.
Proposed by Ben Green and Edward Crane, United Kingdom