\[Стр.\ 36.\]
\[\boxed{\mathbf{4.}}\]
\[\frac{81}{27} = 3\]
\[\frac{144}{9} = 6\]
\[\frac{121}{11} = 11\]
\[\frac{63}{9} = 7\]
\[\boxed{\mathbf{5.}}\]
\[\frac{2}{5} = \frac{4}{10} = \frac{8}{20} = \frac{16}{40} = \frac{48}{120}.\]
\[\boxed{\mathbf{6.}}\]
\[1\ :3 = \frac{1}{3}\ (часть) - расстояния\ \]
\[за\ 1\ час.\]
\[\frac{1}{2}\ :3 = \frac{1}{2} \cdot \frac{1}{3} = \frac{1}{6}\ (часть) -\]
\[пути\ за\ \frac{1}{2}\ ч.\]
\[\frac{1}{4}\ :3 = \frac{1}{4} \cdot \frac{1}{3} = \frac{1}{12}\ (часть) -\]
\[пути\ за\ \frac{1}{4}\ ч.\]
\[\boxed{\mathbf{7.}}\]
\[\textbf{а)}\ \frac{1}{4}\ кг = 250\ г\]
\[250 \cdot 8 = 2000\ (раз).\]
\[2)\ \frac{1}{2}\ кг = 500\ г\]
\[500 \cdot 8 = 4000\ раз.\]
\[\boxed{\mathbf{8.}}\]
\[\textbf{а)}\ \frac{1}{3} = \frac{5}{15} - 5\ долей;\]
\[\textbf{б)}\ \frac{1}{5} = \frac{3}{15} - 3\ доли;\]
\[\textbf{в)}\ \frac{2}{3} = \frac{10}{15} - 10\ долей;\]
\[\textbf{г)}\ \frac{2}{5} = \frac{6}{15} - 6\ долей;\]
\[\textbf{д)}\ \frac{3}{5} = \frac{9}{15} - 9\ долей;\]
\[\textbf{е)}\ \frac{4}{5} = \frac{12}{15} - 12\ долей.\]