At each corner count how many lines meet there.
It works exactly when at most two corners have an odd number - with exactly two you must start at one of them.
The mathematician Leonhard Euler found this rule around 300 years ago while thinking about the bridges of a city.
Example
- yes
- no
For parents
What does this exercise practice?
Drawing in one stroke leads playfully to a real mathematical rule: try first, then discover the pattern.
Common pitfalls
What counts is only whether it is possible at all - not whether you manage it on the first try. Try several starting corners before ticking no.
How to practice at home
Draw the house in one stroke while counting the eight lines out loud - eight syllables, eight strokes.