Identification numbers with check digit algorithms 
Instructions
1. Move the green dot above to choose the module. For example, for module \(9\), place dot as follows:
2. In case you want to multiply \(3\) by \(5\) module \(9\), place the top orange point in line \(3\) and column \(5\). Then, the orange dot below points to the result of the product. In the figure above, it is \(6\).
