Putnam 2013 A1
- Session A
Recall that a regular icosahedron is a convex polyhedron having 12 vertices and 20 faces; the faces are congruent equilateral triangles. On each face of a regular icosahedron is written a nonnegative integer such that the sum of all 20 integers is 39. Show that there are two faces that share a vertex and have the same integer written on them.
Curated text Kedlaya Putnam archive. Quoted with source.
Solutions
Human solution Solution 1 by Kiran Kedlaya and Lenny Ng
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