ГДЗ по математике 4 класс Петерсон рабочая тетрадь Часть 1, 2, 3 Часть 2 | Страница 28

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\[\boxed{\mathbf{1.}}\]

\[a + 0 = a\]

\[0 + a = a\]

\[a - 0 = a\]

\[a - a = 0\]

\[a + b = b + c\]

\[(a + b) + c = a + (b + c)\]

\[\left( 3\frac{2}{5} - 3\frac{2}{5} \right) + \left( 1\frac{3}{4} - 0 \right) =\]

\[= 0 + 1\frac{3}{4} = 1\frac{3}{4}\]

\[\left( 1\frac{6}{17} + 2\frac{4}{5} \right) + 5\frac{11}{17} =\]

\[= \left( 1\frac{6}{17} + 5\frac{11}{17} \right) + 2\frac{4}{5} =\]

\[= 6\frac{17}{17} + 2\frac{4}{5} = 7 + 2\frac{4}{5} = 9\frac{4}{5}\]

\[\boxed{\mathbf{2.}}\]

\[a - (b + c) = (a - b) - c =\]

\[= a - b - c\]

\[(a + b) - c = (a - \ c) + b =\]

\[= a + (b - c)\]

\[18\frac{5}{79} - \left( 17\frac{5}{79} + \frac{3}{4} \right) =\]

\[= \left( 18\frac{5}{79} - 17\frac{5}{79} \right) - \frac{3}{4} = 1 - \frac{3}{4} =\]

\[= \frac{4}{4} - \frac{3}{4} = \frac{1}{4}\]

\[\left( 5\frac{8}{43} + \frac{7}{8} \right) - 3\frac{8}{43} =\]

\[= \left( 5\frac{8}{43} - 3\frac{8}{43} \right) + \frac{7}{8} = 2 + \frac{7}{8} =\]

\[= 2\frac{7}{8}\]

\[\boxed{\mathbf{3.}}\]

\[\textbf{а)}\ 3\frac{19}{24} + \left( 5\frac{1}{9} + 1\frac{5}{24} \right) =\]

\[= \left( 3\frac{19}{24} + 1\frac{5}{24} \right) + 5\frac{1}{9} =\]

\[= 4\frac{24}{24} + 5\frac{1}{9} = 5 + 5\frac{1}{9} = 10\frac{1}{9}\]

\[\textbf{б)}\ \left( 1\frac{5}{8} + 4\frac{8}{17} \right) + \left( \frac{9}{17} + 2\frac{3}{8} \right) =\]

\[= \left( 1\frac{5}{8} + 2\frac{3}{8} \right) + \left( 4\frac{8}{17} + \frac{9}{17} \right) =\]

\[= 3\frac{8}{8} + 4\frac{17}{17} = 4 + 5 = 9\]

\[\textbf{в)}\ 7\frac{16}{35} - \left( 3\frac{11}{35} + 4\frac{1}{35} \right) =\]

\[= 7\frac{16}{35} - 7\frac{12}{35} = \frac{4}{35}\]

\[\textbf{г)}\ \left( 4\frac{56}{789} + 1\frac{5}{6} \right) - 4\frac{56}{789} =\]

\[= \left( 4\frac{56}{789} - 4\frac{56}{789} \right) + 1\frac{5}{6} =\]

\[= 0 + 1\frac{5}{6} = 1\frac{5}{6}\]

\[\textbf{д)}\ \left( 1\frac{6}{11} + 5\frac{16}{39} \right) - 2\frac{16}{39} =\]

\[= 1\frac{6}{11} + \left( 5\frac{16}{39} - 2\frac{16}{39} \right) =\]

\[= 1\frac{6}{11} + 3 = 4\frac{6}{11}\]

\[\textbf{е)}\ 7\frac{13}{14} - \left( 2\frac{13}{14} + 4\frac{17}{25} \right) =\]

\[= \left( 7\frac{13}{14} - 2\frac{13}{14} \right) - 4\frac{17}{25} =\]

\[= 5 - 4\frac{17}{25} = 4\frac{25}{25} - 4\frac{17}{25} = \frac{8}{25}\]

\[\boxed{\mathbf{4.}}\]

\[\textbf{а)}\ 1\ м = \frac{1}{1000}\ км\]

\[58\ м = \frac{58}{1000}\ км\]

\[49\ см = \frac{49}{100\ 000}\ км\]

\[\textbf{б)}\ 1\ см^{2} = \frac{1}{100}\ дм^{2}\]

\[35\ см^{2} = \frac{35}{100}\ дм^{2}\]

\[74\ мм^{2} = \frac{74}{10000}\ дм^{2}\]

\[\textbf{в)}\ 1\ кг = \frac{1}{100}\ ц\]

\[9\ кг = \frac{9}{100}\ ц\]

\[21\ г = \frac{21}{100000}\ ц\]

\[\textbf{г)}\ 1\ ч = \frac{1}{24}\ сут\]

\[5\ ч = \frac{5}{24}\ сут\]

\[32\ мин = \frac{32}{60 \cdot 24}\ сут =\]

\[= \frac{32}{1440}\ сут\]