№1. Выполните действия: A) 3 4 ⋅ 8 9 7 Б) 15 ⋅ 25 5 B) 1:12 18 5 Г) 35⋅ 9 5 10 Д) 611 7 E) 12:21 4 Ж) 615 3)8:2

А) \[\frac{3}{8} \cdot \frac{4}{9} = \frac{3 \cdot 4}{8 \cdot 9} = \frac{12}{72} = \frac{1}{6}\]

Б) \[\frac{7}{15} \cdot 25 = \frac{7 \cdot 25}{15} = \frac{7 \cdot 5}{3} = \frac{35}{3} = 11\frac{2}{3}\]

В) \[1 \frac{5}{12} = \frac{1 \cdot 12 + 5}{12} = \frac{17}{12}\] \[\frac{17}{12} : \frac{18}{1} = \frac{17}{12} \cdot \frac{1}{18} = \frac{17}{216}\]

Г) \[\frac{18}{35} \cdot \frac{5}{9} = \frac{18 \cdot 5}{35 \cdot 9} = \frac{2 \cdot 1}{7 \cdot 1} = \frac{2}{7}\]

Д) \[\frac{5}{6} : \frac{10}{11} = \frac{5}{6} \cdot \frac{11}{10} = \frac{1 \cdot 11}{6 \cdot 2} = \frac{11}{12}\]

Е) \[\frac{7}{12} : 21 = \frac{7}{12} \cdot \frac{1}{21} = \frac{1 \cdot 1}{12 \cdot 3} = \frac{1}{36}\]

Ж) \[6 \cdot \frac{4}{15} = \frac{6 \cdot 4}{15} = \frac{24}{15} = \frac{8}{5} = 1\frac{3}{5}\]

З) \[8 : \frac{2}{5} = 8 \cdot \frac{5}{2} = \frac{8 \cdot 5}{2} = \frac{40}{2} = 20\]