\[\boxed{\mathbf{3.}\mathbf{81}}\]
Пояснение.
Решение.
\[\textbf{а)}\ 21\ 700\ :10 = 2170\]
\[\textbf{б)}\ 6\ 123\ 000\ :100 = 61\ 230\]
\[\textbf{в)}\ 290\ 000\ :1000 = 290\]
\[\textbf{г)}\ 204\ 400\ :200 =\]
\[= 204\ 400\ :100\ :2 =\]
\[= 2044\ :2 = 1022\]