The Seven Bridges of Königsberg

Step 3: Euler Gets a Letter

In 1736 Leonhard Euler proved no walk could cross Königsberg's seven bridges exactly once, and invented graph theory doing it. Try the puzzle yourself, then see Euler's trick.

1. A Sunday Puzzle
2. Try It Yourself
3. Euler Gets a Letter
4. Dots and Lines
5. The Rule
6. What It Started