П.20 Выполните действие: a) 16.9. 27 4 б) 42.55 5 7 7 3 B) 12 12 : 14 7 : г) 55 22

а)

\[\frac{16}{27} : \frac{9}{4} = \frac{16}{27} \cdot \frac{4}{9} = \frac{16 \cdot 4}{27 \cdot 9} = \frac{64}{243}\]

б)

\[\frac{42}{5} : \frac{55}{7} = \frac{42}{5} \cdot \frac{7}{55} = \frac{42 \cdot 7}{5 \cdot 55} = \frac{294}{275}\]

в)

\[\frac{7}{12} : \frac{3}{12} = \frac{7}{12} \cdot \frac{12}{3} = \frac{7 \cdot 12}{12 \cdot 3} = \frac{7 \cdot \cancel{12}}{\cancel{12} \cdot 3} = \frac{7}{3} = 2 \frac{1}{3}\]

г)

\[\frac{14}{55} : \frac{7}{22} = \frac{14}{55} \cdot \frac{22}{7} = \frac{14 \cdot 22}{55 \cdot 7} = \frac{2 \cdot \cancel{7} \cdot 2 \cdot \cancel{11}}{5 \cdot \cancel{11} \cdot \cancel{7}} = \frac{2 \cdot 2}{5} = \frac{4}{5}\]

Ответ: а) \(\frac{64}{243}\); б) \(\frac{294}{275}\); в) \(2 \frac{1}{3}\); г) \(\frac{4}{5}\)