4. Выполните умножение: a) \(\frac{7}{9} \cdot \frac{2}{5}\); б) \(\frac{12}{13} \cdot \frac{26}{27}\); в) \(3 \frac{3}{5} \cdot 2 \frac{1}{12}\); г) \(4 \frac{2}{7} \cdot 2 \frac{4}{5}\); д) \(2 \frac{5}{8} \cdot \frac{4}{21}\); e) \(\frac{6}{7} \cdot 2 \frac{13}{18}\)

4. Выполните умножение: а) \(\frac{7}{9} \cdot \frac{2}{5} = \frac{7 \cdot 2}{9 \cdot 5} = \frac{14}{45}\) б) \(\frac{12}{13} \cdot \frac{26}{27} = \frac{12 \cdot 26}{13 \cdot 27} = \frac{12 \cdot 2}{1 \cdot 27} = \frac{24}{27} = \frac{8}{9}\) в) \(3 \frac{3}{5} \cdot 2 \frac{1}{12} = \frac{18}{5} \cdot \frac{25}{12} = \frac{18 \cdot 25}{5 \cdot 12} = \frac{18 \cdot 5}{1 \cdot 12} = \frac{3 \cdot 5}{1 \cdot 2} = \frac{15}{2} = 7 \frac{1}{2}\) г) \(4 \frac{2}{7} \cdot 2 \frac{4}{5} = \frac{30}{7} \cdot \frac{14}{5} = \frac{30 \cdot 14}{7 \cdot 5} = \frac{6 \cdot 2}{1 \cdot 1} = 12\) д) \(2 \frac{5}{8} \cdot \frac{4}{21} = \frac{21}{8} \cdot \frac{4}{21} = \frac{21 \cdot 4}{8 \cdot 21} = \frac{1 \cdot 1}{2 \cdot 1} = \frac{1}{2}\) е) \(\frac{6}{7} \cdot 2 \frac{13}{18} = \frac{6}{7} \cdot \frac{49}{18} = \frac{6 \cdot 49}{7 \cdot 18} = \frac{1 \cdot 7}{1 \cdot 3} = \frac{7}{3} = 2 \frac{1}{3}\)