Coins on the table form regular polygons
Source: BWM Germany Round 1, 2015 - Problem 1
April 8, 2015
geometrypolygonbundeswettbewerbGermany
Problem Statement
Twelve 1-Euro-coins are laid flat on a table, such that their midpoints form a regular -gon. Adjacent coins are tangent to each other.
Prove that it is possible to put another seven such coins into the interior of the ring of the twelve coins.