All students have used this 'pi' constant at least once. But how many of them really understand what it represents? Although teachers struggle to make this comprehensible, they use the wrong ways!
An optical representation and even more a toy that kids can touch and play, is the best way to learn difficult concepts. In that way, students will never use again the excuse 'I used to know this, but now I forgot'!
The parts are easy to print, fast and low cost! You can use PLA or ABS, with usual printing settings (No support needed).
The formula represented is: [Perimeter of circle = pi * Diameter]