Увеличьте: а) 4/7 в 3 раза

1. a) $\frac{4}{7} \cdot 3 = \frac{12}{7} = 1\frac{5}{7}$ б) $1\frac{3}{8} \cdot 5 = \frac{11}{8} \cdot 5 = \frac{55}{8} = 6\frac{7}{8}$ в) $\frac{2}{9} \cdot 18 = \frac{2 \cdot 18}{9} = \frac{36}{9} = 4$ г) $2\frac{6}{13} \cdot 13 = \frac{32}{13} \cdot 13 = \frac{32 \cdot 13}{13} = 32$ 2. a) $\frac{1}{10}$ км = 100 м : 10 = 100 м б) $\frac{2}{5}$ км = 1000 м$\cdot \frac{2}{5}$ = 400 м в) $\frac{4}{15}$ км = 1000 м$\cdot \frac{4}{15} = \frac{4000}{15}$ м = 266$\frac{2}{3}$ м г) $1\frac{7}{30}$ км = $\frac{37}{30}$ км = 1000 м$\cdot \frac{37}{30} = \frac{3700}{30}$ м = 123$\frac{1}{3}$ м д) $6\frac{3}{55}$ км = $\frac{333}{55}$ км = 1000 м$\cdot \frac{333}{55} = \frac{333000}{55}$ м = 6054$\frac{6}{11}$ м 3. a) $2x + \frac{1}{3}y = 2 \cdot 2\frac{1}{4} + \frac{1}{3} \cdot 9 = 2 \cdot \frac{9}{4} + \frac{1}{3} \cdot 9 = \frac{9}{2} + 3 = 4\frac{1}{2} + 3 = 7\frac{1}{2}$ б) $2\frac{3}{4}x - 1\frac{2}{7}y = \frac{11}{4} \cdot 1\frac{5}{11} - \frac{9}{7} \cdot 1\frac{2}{3} = \frac{11}{4} \cdot \frac{16}{11} - \frac{9}{7} \cdot \frac{5}{3} = \frac{4}{1} - \frac{15}{7} = 4 - 2\frac{1}{7} = 1\frac{6}{7}$ 4. $4\frac{3}{5}m + 9\frac{6}{7}n - 3\frac{1}{5}m - 5\frac{2}{7}n = (4\frac{3}{5} - 3\frac{1}{5})m + (9\frac{6}{7} - 5\frac{2}{7})n = (4 - 3 + \frac{3}{5} - \frac{1}{5})m + (9 - 5 + \frac{6}{7} - \frac{2}{7})n = 1\frac{2}{5}m + 4\frac{4}{7}n = \frac{7}{5} \cdot \frac{11}{14} + \frac{32}{7} \cdot \frac{25}{8} = \frac{1}{5} \cdot \frac{11}{2} + \frac{4}{7} \cdot \frac{25}{1} = \frac{11}{10} + \frac{100}{7} = \frac{77 + 1000}{70} = \frac{1077}{70} = 15\frac{27}{70}$ 5. $S = v \cdot t$ $S = 60\frac{5}{6} \cdot 2\frac{2}{5} = \frac{365}{6} \cdot \frac{12}{5} = \frac{365 \cdot 2}{5} = \frac{730}{5} = 146$ км 6. $S = a \cdot b$ $S = 3\frac{1}{4} \cdot 4\frac{1}{3} = \frac{13}{4} \cdot \frac{13}{3} = \frac{169}{12} = 14\frac{1}{12}$ м$^2$ $14\frac{1}{12} \cdot 120 = \frac{169}{12} \cdot 120 = 169 \cdot 10 = 1690$ г