MathDB
43 friends fror birthday, cake of 15-gon

Source: III May Olympiad (Olimpiada de Mayo) 1997 L1 P5

September 17, 2022
combinatoricscombinatorial geometry

Problem Statement

When Pablo turns 1515, he throws a party inviting 4343 friends. He presents them with a cake n the form of a regular 1515-sided polygon and on it 1515 candles. The candles are arranged so that between candles and vertices there are never three aligned (any three candles are not aligned, nor are any two candles with a vertex of the polygon, nor are any two vertices of the polygon with a candle). Then Pablo divides the cake into triangular pieces, by means of cuts that join candles to each other or candles and vertices, but also do not intersect with others already made. Why, by doing this, Paul was able to distribute a piece to each of his guests but he was left without eating?