2.273 Найдите значение выражения: a) \(\frac{7}{9} \cdot \frac{3}{4} \cdot \frac{5}{21}\); б) \(\frac{2}{5} \cdot \frac{11}{15} \cdot \frac{3}{22}\); в) \(\frac{4}{5} \cdot \frac{7}{20} \cdot \frac{25}{28}\); г) \(\frac{125}{149} \cdot \frac{8}{11} \cdot \frac{121}{1000}\)

a)

$$ \frac{7}{9} \cdot \frac{3}{4} \cdot \frac{5}{21} = \frac{7 \cdot 3 \cdot 5}{9 \cdot 4 \cdot 21} = \frac{105}{756} = \frac{5}{36} $$

б)

$$ \frac{2}{5} \cdot \frac{11}{15} \cdot \frac{3}{22} = \frac{2 \cdot 11 \cdot 3}{5 \cdot 15 \cdot 22} = \frac{66}{1650} = \frac{1}{25} $$

в)

$$ \frac{4}{5} \cdot \frac{7}{20} \cdot \frac{25}{28} = \frac{4 \cdot 7 \cdot 25}{5 \cdot 20 \cdot 28} = \frac{700}{2800} = \frac{1}{4} $$

г)

$$ \frac{125}{149} \cdot \frac{8}{11} \cdot \frac{121}{1000} = \frac{125 \cdot 8 \cdot 121}{149 \cdot 11 \cdot 1000} = \frac{125 \cdot 8 \cdot 11}{149 \cdot 1000} = \frac{11000}{149000} = \frac{11}{149} $$

Ответ: а) \(\frac{5}{36}\); б) \(\frac{1}{25}\); в) \(\frac{1}{4}\); г) \(\frac{11}{149}\)