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

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

A Swastikaland Map

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?

Solution

It would have been $2$, but for the glitch at the bottom left hand corner, where there happen to be three adjoining regions.

Thus $3$ colours are needed.

Sources

• 1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Solutions: $213$. -- A Swastikaland Map
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Answers: $443$. A Swastikaland Map