Реши примеры по математике для 7 класса: a) 5/6 + 1/4

- a) $\frac{5}{6} + \frac{1}{4} = \frac{5 \cdot 2}{6 \cdot 2} + \frac{1 \cdot 3}{4 \cdot 3} = \frac{10}{12} + \frac{3}{12} = \frac{10+3}{12} = \frac{13}{12} = 1\frac{1}{12}$ - б) $\frac{7}{8} - \frac{5}{6} = \frac{7 \cdot 3}{8 \cdot 3} - \frac{5 \cdot 4}{6 \cdot 4} = \frac{21}{24} - \frac{20}{24} = \frac{21-20}{24} = \frac{1}{24}$ - в) $\frac{3}{10} - \frac{4}{15} = \frac{3 \cdot 3}{10 \cdot 3} - \frac{4 \cdot 2}{15 \cdot 2} = \frac{9}{30} - \frac{8}{30} = \frac{9-8}{30} = \frac{1}{30}$ - г) $5 - 3\frac{2}{7} = 4\frac{7}{7} - 3\frac{2}{7} = (4-3) + (\frac{7}{7} - \frac{2}{7}) = 1 + \frac{7-2}{7} = 1\frac{5}{7}$ - д) $\frac{4}{9} \cdot \frac{3}{8} = \frac{4 \cdot 3}{9 \cdot 8} = \frac{12}{72} = \frac{1}{6}$ - e) $\frac{5}{8} : \frac{9}{10} = \frac{5}{8} \cdot \frac{10}{9} = \frac{5 \cdot 10}{8 \cdot 9} = \frac{50}{72} = \frac{25}{36}$ - ж) $2\frac{6}{7} : 1\frac{3}{7} = \frac{2 \cdot 7 + 6}{7} : \frac{1 \cdot 7 + 3}{7} = \frac{14+6}{7} : \frac{7+3}{7} = \frac{20}{7} : \frac{10}{7} = \frac{20}{7} \cdot \frac{7}{10} = \frac{20 \cdot 7}{7 \cdot 10} = \frac{140}{70} = 2$ - з) $6\frac{3}{5} \cdot 10 = \frac{6 \cdot 5 + 3}{5} \cdot 10 = \frac{30+3}{5} \cdot 10 = \frac{33}{5} \cdot 10 = \frac{33 \cdot 10}{5} = \frac{330}{5} = 66$ **Ответы:** - a) $1\frac{1}{12}$ - б) $\frac{1}{24}$ - в) $\frac{1}{30}$ - г) $1\frac{5}{7}$ - д) $\frac{1}{6}$ - e) $\frac{25}{36}$ - ж) $2$ - з) $66$