Выполните действие: 3 a) 7 ⋅ 14 ; 39 б) 1 11 ⋅ 1 5 ; 24 7 в) 2 3 ⋅ 4 4 ; 16 5 7 г) 11 ⋅ 5 33

a) $$ \frac{3}{7} \cdot \frac{14}{39} = \frac{3 \cdot 14}{7 \cdot 39} = \frac{3 \cdot 2 \cdot 7}{7 \cdot 3 \cdot 13} = \frac{2}{13} $$

б) $$ 1\frac{11}{24} \cdot 1\frac{5}{7} = \frac{1 \cdot 24 + 11}{24} \cdot \frac{1 \cdot 7 + 5}{7} = \frac{35}{24} \cdot \frac{12}{7} = \frac{35 \cdot 12}{24 \cdot 7} = \frac{5 \cdot 7 \cdot 12}{12 \cdot 2 \cdot 7} = \frac{5}{2} = 2\frac{1}{2} $$

в) $$ 2\frac{3}{16} \cdot 4\frac{4}{5} = \frac{2 \cdot 16 + 3}{16} \cdot \frac{4 \cdot 5 + 4}{5} = \frac{35}{16} \cdot \frac{24}{5} = \frac{35 \cdot 24}{16 \cdot 5} = \frac{7 \cdot 5 \cdot 8 \cdot 3}{8 \cdot 2 \cdot 5} = \frac{7 \cdot 3}{2} = \frac{21}{2} = 10\frac{1}{2} $$

г) $$ 11 \cdot 5\frac{7}{33} = 11 \cdot \frac{5 \cdot 33 + 7}{33} = 11 \cdot \frac{165 + 7}{33} = 11 \cdot \frac{172}{33} = \frac{11 \cdot 172}{33} = \frac{11 \cdot 172}{11 \cdot 3} = \frac{172}{3} = 57\frac{1}{3} $$

Ответ: а) $$ \frac{2}{13} $$, б) $$ 2\frac{1}{2} $$, в) $$10\frac{1}{2} $$, г) $$ 57\frac{1}{3} $$