\[Стр.\ 25.\]
\[\boxed{\mathbf{7.}}\]
\[Увеличилась\ на\ 4\ \frac{м}{с}.\]
\[\boxed{\mathbf{8.}}\]
\[\textbf{а)}\ 1,6 \cdot 0,25 = 1,6\ :4 =\]
\[= 0,4 + 3,6 = 4\ :0,8 = 40\ :8 =\]
\[= 5\]
\[\textbf{б)}\ 1,2 \cdot 7 = 8,4 + 1,6 =\]
\[= 10\ :0,01 = 1000\ :1 = 1000\]
\[\textbf{в)}\ 0,7 \cdot 0,7 = 0,49 + 0,51 =\]
\[= 1\ :0,2 = 10\ :2 = 5\]
\[\textbf{г)}\ 2,4 \cdot 0,5 = 1,2 + 6,6 =\]
\[= 7,8\ :0,3 = 78\ :3 = 26\]
\[\boxed{\mathbf{9.}}\]
\[\textbf{а)}\frac{7}{12}\ :3\frac{1}{16} = \frac{7 \cdot 16}{12 \cdot 49} = \frac{4}{21}\]
\[\textbf{б)}\ 32\ :9\frac{3}{5} = \frac{32 \cdot 5}{48} = \frac{10}{3} = 3\frac{1}{3}\]
\[\textbf{в)}\ 204\frac{1}{4} + \frac{1}{32} = 204\frac{8}{32} + \frac{1}{32} =\]
\[= 204\frac{9}{32}\]
\[\textbf{г)}\ 2\frac{1}{4} \cdot 2\frac{2}{3} = \frac{9 \cdot 8}{4 \cdot 3} = 3 \cdot 2 = 6\]