Решите примеры на умножение обыкновенных дробей.

Для умножения дробей нужно перемножить их числители и знаменатели. Перед умножением стоит сократить дроби. **Столбец 1** 1. $\frac{2}{5} \cdot \frac{3}{4} = \frac{2 \cdot 3}{5 \cdot 4} = \frac{1 \cdot 3}{5 \cdot 2} = \frac{3}{10}$ 2. $\frac{1}{7} \cdot \frac{2}{3} = \frac{2}{21}$ 3. $\frac{4}{5} \cdot \frac{6}{5} = \frac{24}{25}$ 4. $\frac{1}{8} \cdot \frac{7}{9} = \frac{7}{72}$ 5. $\frac{2}{3} \cdot \frac{6}{7} = \frac{2 \cdot 6}{3 \cdot 7} = \frac{2 \cdot 2}{1 \cdot 7} = \frac{4}{7}$ 6. $\frac{5}{6} \cdot \frac{4}{10} = \frac{5 \cdot 4}{6 \cdot 10} = \frac{1 \cdot 2}{3 \cdot 2} = \frac{1}{3}$ 7. $\frac{11}{14} \cdot \frac{7}{22} = \frac{11 \cdot 7}{14 \cdot 22} = \frac{1 \cdot 1}{2 \cdot 2} = \frac{1}{4}$ 8. $\frac{4}{15} \cdot \frac{5}{8} = \frac{4 \cdot 5}{15 \cdot 8} = \frac{1 \cdot 1}{3 \cdot 2} = \frac{1}{6}$ 9. $\frac{3}{10} \cdot \frac{2}{6} = \frac{3 \cdot 2}{10 \cdot 6} = \frac{1 \cdot 1}{5 \cdot 2} = \frac{1}{10}$ 10. $\frac{17}{33} \cdot \frac{11}{34} = \frac{17 \cdot 11}{33 \cdot 34} = \frac{1 \cdot 1}{3 \cdot 2} = \frac{1}{6}$ 11. $\frac{7}{30} \cdot \frac{6}{21} = \frac{7 \cdot 6}{30 \cdot 21} = \frac{1 \cdot 1}{5 \cdot 3} = \frac{1}{15}$ 12. $\frac{4}{12} \cdot \frac{18}{20} = \frac{1}{3} \cdot \frac{9}{10} = \frac{3}{10}$ 13. $\frac{21}{25} \cdot \frac{15}{42} = \frac{21 \cdot 15}{25 \cdot 42} = \frac{1 \cdot 3}{5 \cdot 2} = \frac{3}{10}$ **Столбец 2** 1. $\frac{4}{5} \cdot \frac{1}{2} = \frac{2}{5}$ 2. $\frac{3}{7} \cdot \frac{6}{7} = \frac{18}{49}$ 3. $\frac{1}{2} \cdot \frac{3}{4} = \frac{3}{8}$ 4. $\frac{5}{7} \cdot \frac{5}{7} = \frac{25}{49}$ 5. $\frac{8}{11} \cdot \frac{16}{77} = \frac{128}{847}$ 6. $\frac{5}{23} \cdot \frac{15}{46} = \frac{75}{1058}$ 7. $\frac{14}{25} \cdot \frac{21}{50} = \frac{294}{1250} = \frac{147}{625}$ 8. $\frac{18}{20} \cdot \frac{27}{40} = \frac{9}{10} \cdot \frac{27}{40} = \frac{243}{400}$ 9. $\frac{63}{70} \cdot \frac{81}{270} = \frac{9}{10} \cdot \frac{3}{10} = \frac{27}{100}$ 10. $\frac{2}{33} \cdot \frac{24}{30} = \frac{2 \cdot 24}{33 \cdot 30} = \frac{2 \cdot 4}{11 \cdot 15} = \frac{8}{165}$ 11. $\frac{75}{150} \cdot \frac{5}{50} = \frac{1}{2} \cdot \frac{1}{10} = \frac{1}{20}$ 12. $\frac{3}{20} \cdot \frac{17}{10} = \frac{51}{200}$ 13. $\frac{8}{11} \cdot \frac{4}{99} = \frac{32}{1089}$ **Столбец 3** 1. $\frac{5}{7} \cdot \frac{21}{15} \cdot \frac{9}{24} = (\frac{5 \cdot 21}{7 \cdot 15}) \cdot \frac{3}{8} = 1 \cdot \frac{3}{8} = \frac{3}{8}$ 2. $\frac{4}{5} \cdot \frac{8}{10} \cdot \frac{20}{2} = \frac{4}{5} \cdot \frac{4}{5} \cdot 10 = \frac{16}{25} \cdot 10 = \frac{32}{5} = 6\frac{2}{5}$ 3. $\frac{6}{7} \cdot \frac{3}{9} \cdot \frac{28}{30} = (\frac{6 \cdot 28}{7 \cdot 30}) \cdot \frac{1}{3} = (\frac{1 \cdot 4}{1 \cdot 5}) \cdot \frac{1}{3} = \frac{4}{15}$ 4. $\frac{40}{50} \cdot \frac{20}{5} \cdot \frac{3}{4} = \frac{4}{5} \cdot 4 \cdot \frac{3}{4} = \frac{4}{5} \cdot 3 = \frac{12}{5} = 2\frac{2}{5}$ 5. $\frac{17}{20} \cdot \frac{10}{34} \cdot \frac{5}{2} = (\frac{17 \cdot 10}{20 \cdot 34}) \cdot \frac{5}{2} = \frac{1}{4} \cdot \frac{5}{2} = \frac{5}{8}$ 6. $\frac{15}{20} \cdot \frac{150}{200} \cdot \frac{2}{3} = \frac{3}{4} \cdot \frac{3}{4} \cdot \frac{2}{3} = \frac{3}{8}$ 7. $\frac{14}{63} \cdot \frac{18}{28} \cdot \frac{2}{6} = (\frac{14 \cdot 18}{63 \cdot 28}) \cdot \frac{1}{3} = (\frac{1 \cdot 2}{7 \cdot 2}) \cdot \frac{1}{3} = \frac{1}{7} \cdot \frac{1}{3} = \frac{1}{21}$ 8. $\frac{77}{25} \cdot \frac{11}{13} \cdot \frac{65}{7} = (\frac{77 \cdot 65}{25 \cdot 7}) \cdot \frac{11}{13} = (\frac{11 \cdot 13}{5 \cdot 1}) \cdot \frac{11}{13} = \frac{121}{5} = 24\frac{1}{5}$ 9. $\frac{81}{90} \cdot \frac{2}{3} \cdot \frac{18}{20} = \frac{9}{10} \cdot \frac{2}{3} \cdot \frac{9}{10} = \frac{3}{5} \cdot \frac{9}{10} = \frac{27}{50}$ 10. $\frac{42}{60} \cdot \frac{7}{12} \cdot \frac{3}{21} = \frac{7}{10} \cdot \frac{7}{12} \cdot \frac{1}{7} = \frac{7}{120}$ 11. $\frac{8}{15} \cdot \frac{12}{120} \cdot \frac{30}{40} = \frac{8}{15} \cdot \frac{1}{10} \cdot \frac{3}{4} = \frac{2}{15} \cdot \frac{3}{10} = \frac{1}{25}$ 12. $\frac{4}{3} \cdot \frac{12}{20} \cdot \frac{1}{5} = \frac{4}{3} \cdot \frac{3}{5} \cdot \frac{1}{5} = \frac{4}{25}$ 13. $\frac{6}{10} \cdot \frac{5}{44} \cdot \frac{2}{11} = \frac{3}{5} \cdot \frac{5}{44} \cdot \frac{2}{11} = \frac{3}{44} \cdot \frac{2}{11} = \frac{3}{242}$