Решите примеры на умножение и деление обыкновенных дробей.

**Ответы:** **Первый столбик (умножение):** 1. $\frac{2}{5} \cdot \frac{3}{4} = \frac{2 \cdot 3}{5 \cdot 4} = \frac{1 \cdot 3}{5 \cdot 2} = \mathbf{\frac{3}{10}}$ 2. $\frac{1}{7} \cdot \frac{2}{3} = \frac{1 \cdot 2}{7 \cdot 3} = \mathbf{\frac{2}{21}}$ 3. $\frac{4}{5} \cdot \frac{6}{5} = \frac{4 \cdot 6}{5 \cdot 5} = \mathbf{\frac{24}{25}}$ 4. $\frac{1}{8} \cdot \frac{7}{9} = \frac{1 \cdot 7}{8 \cdot 9} = \mathbf{\frac{7}{72}}$ 5. $\frac{2}{3} \cdot \frac{6}{7} = \frac{2 \cdot 6}{3 \cdot 7} = \frac{2 \cdot 2}{1 \cdot 7} = \mathbf{\frac{4}{7}}$ 6. $\frac{5}{6} \cdot \frac{4}{10} = \frac{5 \cdot 4}{6 \cdot 10} = \frac{1 \cdot 2}{3 \cdot 2} = \mathbf{\frac{1}{3}}$ 7. $\frac{11}{14} \cdot \frac{7}{22} = \frac{11 \cdot 7}{14 \cdot 22} = \frac{1 \cdot 1}{2 \cdot 2} = \mathbf{\frac{1}{4}}$ 8. $\frac{4}{15} \cdot \frac{5}{8} = \frac{4 \cdot 5}{15 \cdot 8} = \frac{1 \cdot 1}{3 \cdot 2} = \mathbf{\frac{1}{6}}$ 9. $\frac{3}{10} \cdot \frac{2}{6} = \frac{3 \cdot 2}{10 \cdot 6} = \frac{1 \cdot 1}{5 \cdot 2} = \mathbf{\frac{1}{10}}$ 10. $\frac{17}{33} \cdot \frac{11}{34} = \frac{17 \cdot 11}{33 \cdot 34} = \frac{1 \cdot 1}{3 \cdot 2} = \mathbf{\frac{1}{6}}$ **Второй столбик (деление):** 1. $\frac{4}{5} : \frac{1}{2} = \frac{4}{5} \cdot \frac{2}{1} = \mathbf{\frac{8}{5} = 1\frac{3}{5}}$ 2. $\frac{3}{7} : \frac{6}{7} = \frac{3}{7} \cdot \frac{7}{6} = \frac{3 \cdot 7}{7 \cdot 6} = \mathbf{\frac{1}{2}}$ 3. $\frac{1}{2} : \frac{3}{4} = \frac{1}{2} \cdot \frac{4}{3} = \frac{1 \cdot 4}{2 \cdot 3} = \mathbf{\frac{2}{3}}$ 4. $\frac{5}{7} : \frac{5}{7} = \frac{5}{7} \cdot \frac{7}{5} = \mathbf{1}$ 5. $\frac{8}{11} : \frac{16}{77} = \frac{8}{11} \cdot \frac{77}{16} = \frac{8 \cdot 77}{11 \cdot 16} = \frac{1 \cdot 7}{1 \cdot 2} = \mathbf{\frac{7}{2} = 3\frac{1}{2}}$ 6. $\frac{5}{23} : \frac{15}{46} = \frac{5}{23} \cdot \frac{46}{15} = \frac{5 \cdot 46}{23 \cdot 15} = \frac{1 \cdot 2}{1 \cdot 3} = \mathbf{\frac{2}{3}}$ 7. $\frac{14}{25} : \frac{21}{50} = \frac{14}{25} \cdot \frac{50}{21} = \frac{14 \cdot 50}{25 \cdot 21} = \frac{2 \cdot 2}{1 \cdot 3} = \mathbf{\frac{4}{3} = 1\frac{1}{3}}$ 8. $\frac{18}{20} : \frac{27}{40} = \frac{18}{20} \cdot \frac{40}{27} = \frac{18 \cdot 40}{20 \cdot 27} = \frac{2 \cdot 2}{1 \cdot 3} = \mathbf{\frac{4}{3} = 1\frac{1}{3}}$ 9. $\frac{63}{70} : \frac{81}{270} = \frac{63}{70} \cdot \frac{270}{81} = \frac{63 \cdot 270}{70 \cdot 81} = \frac{63 \cdot 27}{7 \cdot 81} = \frac{9 \cdot 1}{1 \cdot 3} = \mathbf{3}$ 10. $\frac{2}{33} : \frac{24}{30} = \frac{2}{33} \cdot \frac{30}{24} = \frac{2 \cdot 30}{33 \cdot 24} = \frac{1 \cdot 10}{33 \cdot 12} = \frac{1 \cdot 5}{33 \cdot 6} = \mathbf{\frac{5}{198}}$