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Figure This!



Four colors.




Complete Solution:


The least number of colors needed for this map is four. One possible solution, shown in Figure 1 at right, uses the colors red, green, yellow and blue.

fig. 1

It is not possible to use fewer than four colors. If a state is surrounded by an even number of states, alternate two colors as you move around the states. The surrounded state will require a third color, as in Figure 2 at right.

fig. 2

If a state is surrounded by an odd number of states, the surrounding states require three colors, and the surrounded state requires the fourth color. See Figure 3.


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