"Einfach klasse in Mathematik, 1. und 2. Klasse" and "Einfach klasse in Mathematik, 3. und 4. Klasse" are kind of interactive versions of "Einfach klasse in..." books developed for primary school and published by Duden Verlag. Special feature of the both titles is that the material is divided into 3 sections: "Know" - "Train" - "Can". This 3-steps approach helps kids to organize their learning and find necessary information quickly. Each product offers hundreds of tasks developed in cooperation with school teachers. Lovely illustrations, user-friendly navigation and motivating atmosphere turn mathematics into an exciting adventure. The product was developed by The Web Production for Cornelsen Verlag and Duden Verlag.