MathDB
AGMC 2021 Prelim Q2

Source:

January 10, 2023
geometrycongruent triangles

Problem Statement

The winners of first AGMC in 2019 gifts the person in charge of the organiser, which is a polyhedron formed by 6060 congruent triangles. From the photo, we can see that this polyhedron formed by 6060 quadrilateral spaces. (Note: You can find the photo in 3.4 of https://files.alicdn.com/tpsservice/18c5c7b31a7074edc58abb48175ae4c3.pdf?spm=a1zmmc.index.0.0.51c0719dNAbw3C&file=18c5c7b31a7074edc58abb48175ae4c3.pdf) A quadrilateral space is the plane figures that we fold the figures following the diagonal on a nn sides on a plane (i.e. form an appropriate dihedral angle in where the chosen diagonal is). "Two figure spaces are congruent" means they can coincide completely by isometric transform in R3\mathbb{R}^3. A polyhedron is the bounded space region, whose boundary is formed by the common edge of finite polygon. (a) We know that 2021=43×472021=43\times 47. Does there exist a polyhedron, whose surface can be formed by 4343 congruent 4747-gon? (b) Prove your answer in (a) with logical explanation.