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Graph TheorySuperchallengeGraph Coloring

Graph Coloring · Superchallenge problem

A planar triangulation (every face, including the unbounded one, is a triangle) has 1212 vertices. By the planar edge bound (tight for triangulations), it has 3(12)−6=303(12)-6=30 edges. What is the sum of the degrees of all 1212 vertices?