Henry Ernest Dudeney/Puzzles and Curious Problems/213 - A Swastikaland Map

Puzzles and Curious Problems by Henry Ernest Dudeney: $213$

A Swastikaland Map

Here is a puzzle that the reader will probably think he has solved at almost the first glance.

But will he be correct?

Swastikaland is divided in the manner shown in our illustration.

The Lord High Keeper of the Maps was ordered so to colour this map of the country

that there should be a different colour on each side of every boundary line.

What was the smallest number of colours that he required?

Sources

• 1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Geometrical Problems: Various Geometrical Puzzles: $213$. -- A Swastikaland Map
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Combinatorial & Topological Problems: Map Coloring Puzzles: $443$. A Swastikaland Map