Das Trachtenberg-Geschwindigkeitssystem der grundlegenden Mathematik von Jakow Trachtenberg (Englisch
159,14 €
By Jakow Trachtenberg. Author Jakow Trachtenberg. The Trachtenberg Speed System of Basic Mathematics. It looks like magic, but the rules are based on sound logic. Once one has mastered the rules, lightning calculation is as easy as reading a story.
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