\[\boxed{\mathbf{Вариант\ 1.}}\]
\[\boxed{\mathbf{1.}}\]
\[1)\ \]
\[2)\ 4\ км\ 16\ м \cdot 5 = 20\ км\ 80\ м\]
\[6\ дм\ 7\ см \cdot 8 = 48\ дм\ 56\ см =\]
\[= 53\ дм\ 6\ см\]
\[\boxed{\mathbf{2.}}\]
\[x \cdot 8 = 400\ :10\]
\[x \cdot 8 = 40\]
\[x = 40\ :8\]
\[x = 5\]
\[Проверка:\]
\[5 \cdot 8 = 400\ :10\]
\[40 = 40.\]
\[\boxed{\mathbf{3.}}\]
\[106 \cdot 7 = 742\]