\[Страница\ 16.\]
\[\boxed{\mathbf{12.}}\]
\[\frac{1}{2}\ км = 500\ м.\]
\[\boxed{\mathbf{13.}}\]
\[92\ :4 \cdot 3 = 23 \cdot 3 = 69\ (км) -\]
\[пролетит\ почтовый\ голубь.\]
\[Ответ:69\ км.\]
\[\boxed{\mathbf{14.}}\]
\[12 \cdot 4 = 48\ (км) - должен\ был\ \]
\[проехать\ велосипедист.\]
\[Ответ:48\ км.\]
\[\boxed{\mathbf{15.}}\]
\[2\ см \cdot 3 = 6\ (см) - длина\ \]
\[всего\ отрезка.\]
\[Ответ:6\ см.\]
\[\boxed{\mathbf{16.}}\]
\[\textbf{а)}\ \frac{5}{a};\ \frac{a}{11}:\]
\[a = \left\{ 6;7;8;9;10 \right\}.\]
\[\textbf{б)}\ \frac{a}{13};\ \frac{14}{a}:\]
\[a = \left\{ 13;14 \right\}.\]
\[\textbf{в)}\ \frac{8}{a};\ \frac{a}{12}:\]
\[a = \left\{ 9;10;11 \right\}.\]
\[\textbf{г)}\ \frac{12}{a};\ \frac{a}{8}:\]
\[a = \left\{ 8;9;10;11;12 \right\}.\]
\[\boxed{\mathbf{17.}}\]
\[\textbf{а)}\ \frac{1}{2} < \frac{a}{10} < 1\]
\[\frac{5}{10} < \frac{a}{10} < 1\]
\[a = 6;7;8;9.\]
\[\textbf{б)}\ \frac{1}{3} < \frac{a}{6} < 1\]
\[\frac{2}{6} < \frac{a}{6} < 1\]
\[a = 3;4;5.\]
\[\textbf{в)}\ \frac{1}{6} < \frac{a}{24} < \frac{1}{3}\]
\[\frac{4}{24} < \frac{a}{24} < \frac{8}{24}\ \]
\[a = 5;6;7.\]
\[\textbf{г)}\ \frac{1}{4} < \frac{a}{16} < \frac{1}{2}\]
\[\frac{4}{16} < \frac{a}{16} < \frac{8}{16}\]
\[a = 5;6;7.\ \]