Brain-friendly approaches for a deeper understanding of fraction calculations. Fraction calculations are considered one of the most challenging topics to teach in mathematics education. It is introduced as early as sixth grade, yet students continue to struggle with algebra in higher grades. The insights from Martin Kramer in his new book "Fractions as an Adventure" can help overcome these difficulties. Using gears and chains, both fraction calculations and linear functions can be "grasped" or made visible: - Tactile experiences clarify why the calculation rule "numerator times numerator - denominator times denominator" holds, why "minus times minus equals plus," and why we multiply by the reciprocal to divide fractions. - Concrete learning environments detail a constructivist and brain-friendly approach that promotes sustainable understanding among students.