Вариант 2 1. Найдите значение выражения: 3 11 1 a) 7- : 3-; 12 6 2 5 6) ; 4 2- 15 3,4 B) 20,4 1,71 r) 4 1-

а)\[7\frac{11}{12} : 3\frac{1}{6} = \frac{7 \cdot 12 + 11}{12} : \frac{3 \cdot 6 + 1}{6} = \frac{84 + 11}{12} : \frac{18 + 1}{6} = \frac{95}{12} : \frac{19}{6} = \frac{95}{12} \cdot \frac{6}{19} = \frac{95 \cdot 6}{12 \cdot 19} = \frac{5 \cdot 1}{2 \cdot 1} = \frac{5}{2} = 2\frac{1}{2} = \frac{25}{6}\] б)\[\frac{3\frac{2}{5}}{2\frac{4}{15}} = 3\frac{2}{5} : 2\frac{4}{15} = \frac{3 \cdot 5 + 2}{5} : \frac{2 \cdot 15 + 4}{15} = \frac{15 + 2}{5} : \frac{30 + 4}{15} = \frac{17}{5} : \frac{34}{15} = \frac{17}{5} \cdot \frac{15}{34} = \frac{17 \cdot 15}{5 \cdot 34} = \frac{1 \cdot 3}{1 \cdot 2} = \frac{3}{2} = 1\frac{1}{2} = \frac{15}{14}\] в)\[\frac{3,4}{20,4} = \frac{34}{204} = \frac{17 \cdot 2}{17 \cdot 12} = \frac{2}{12} = \frac{1}{6}\] г)\[\frac{1,71}{4\frac{1}{4}} = 1,71 : 4\frac{1}{4} = 1,71 : \frac{4 \cdot 4 + 1}{4} = 1,71 : \frac{16 + 1}{4} = 1,71 : \frac{17}{4} = \frac{171}{100} : \frac{17}{4} = \frac{171}{100} \cdot \frac{4}{17} = \frac{171 \cdot 4}{100 \cdot 17} = \frac{9 \cdot 1}{25 \cdot 1} = \frac{9}{25} = \frac{171}{56}\]