1. Выполните действие: 12 7 a) 35 18'; 6) 133 115 7 7 7 11 в) 213 115 7 г) 418.9.

a) $$\frac{12}{35} \cdot \frac{7}{18} = \frac{2 \cdot 6}{5 \cdot 7} \cdot \frac{7}{6 \cdot 3} = \frac{2 \cdot \cancel{6}}{5 \cdot \cancel{7}} \cdot \frac{\cancel{7}}{\cancel{6} \cdot 3} = \frac{2}{5 \cdot 3} = \frac{2}{15}$$

Ответ: $$\frac{2}{15}$$

б) $$1\frac{7}{33} \cdot 1\frac{7}{15} = \frac{33+7}{33} \cdot \frac{15+7}{15} = \frac{40}{33} \cdot \frac{22}{15} = \frac{8 \cdot 5}{3 \cdot 11} \cdot \frac{2 \cdot 11}{3 \cdot 5} = \frac{8 \cdot \cancel{5}}{3 \cdot \cancel{11}} \cdot \frac{2 \cdot \cancel{11}}{3 \cdot \cancel{5}} = \frac{8 \cdot 2}{3 \cdot 3} = \frac{16}{9} = 1\frac{7}{9}$$

Ответ: $$1\frac{7}{9}$$

в) $$2\frac{7}{13} \cdot 1\frac{11}{15} = \frac{2\cdot 13 + 7}{13} \cdot \frac{1\cdot 15 + 11}{15} = \frac{26+7}{13} \cdot \frac{15+11}{15} = \frac{33}{13} \cdot \frac{26}{15} = \frac{3 \cdot 11}{13} \cdot \frac{2 \cdot 13}{3 \cdot 5} = \frac{\cancel{3} \cdot 11}{\cancel{13}} \cdot \frac{2 \cdot \cancel{13}}{\cancel{3} \cdot 5} = \frac{11 \cdot 2}{5} = \frac{22}{5} = 4\frac{2}{5}$$

Ответ: $$4\frac{2}{5}$$

г) $$4\frac{7}{18} \cdot 9 = \frac{4\cdot 18 + 7}{18} \cdot 9 = \frac{72+7}{18} \cdot 9 = \frac{79}{18} \cdot 9 = \frac{79}{\cancel{9} \cdot 2} \cdot \cancel{9} = \frac{79}{2} = 39\frac{1}{2}$$

Ответ: $$39\frac{1}{2}$$