\[\boxed{\text{194.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[Работа\ с\ рисунком\ 7.\]
\[\textbf{а)}\ v = 80\ \frac{км}{ч}:\ \]
\[t = 1\ ч.\]
\[v = 25\ \frac{км}{ч}:\]
\[t = 3,8\ ч.\]
\[v = 40\ \frac{км}{ч}:\ \]
\[t = 2,5\ ч.\]
\[\textbf{б)}\ t = 1\ ч:\]
\[v = 80\ \frac{км}{ч}\text{.\ }\]
\[t = 4\ ч:\]
\[v = 22,5\ \frac{км}{ч}\text{\ .}\]
\[t = 8\ ч:\]
\[v = 11\ \frac{км}{ч}\text{.\ }\]
\[t = 16\ ч:\]
\[v = 4\ \frac{км}{ч}.\]
\[\textbf{в)}\ s_{\text{AB}} = 50 \cdot 2 = 100\ км.\]