The Classic Nine Dots Puzzle

Here is a classic one. The illustration below depicts nine dots in the form of a square. Draw four straight lines in such a way that each dot is crossed out.

The restrictions:

You cannot cross a dot more than once.

You must not retrace any line.

You are not permitted to lift your pencil while drawing the lines.

18 12 24 21 03 01

Solution (Click to Show)

18 12 24 21 04 39.png
I first encountered this puzzle when my second-grade teacher challenged us to solve it. It took me less than a minute to solve it since it quickly occurred to me that he didn’t tell us it’s not permitted to draw the lines outside the dots. At first, I thought he would say that it’s not a valid solution, but he was surprised when I presented my answer to him. He then told me that I got the right answer.Perhaps, it was “thinking outside the dots” in action.

See Also:

The Classic Hourglass Puzzle

Ambiguous Profit


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My name Edmark M. Law. I work as a freelance writer, mainly writing about science and mathematics. I am an ardent hobbyist. I like to read, solve puzzles, play chess, make origami and play basketball. In addition, I dabble in magic, particularly card magic and other sleight-of-hand type magic. I live in Hong Kong. You can find me on Twitter` and Facebook. My email is

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