If three countries on a map all border each other, then the map certainly requires at
Chapter 47, Problem 47.6(choose chapter or problem)
If three countries on a map all border each other, then the map certainly requires at least three colors. (For example, look at Brazil, Venezuela, and Colombia or at France, Germany, and Belgium.) Devise a map in which no three countries border each other, and yet the map cannot be colored with fewer than three colors.
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