\[\boxed{\mathbf{1.}}\]
\[12 \cdot 1000 = 12\ 000\]
\[100 \cdot 500 = 50\ 000\]
\[470\ \cdot 10\ 000 = 4\ 700\ 000\]
\[80 \cdot 900 = 72\ 000\]
\[7 \cdot 3000 = 21\ 000\]
\[80\ 000 \cdot 120 = 9\ 600\ 000\]
\[\boxed{\mathbf{2.}}\]
\[16 \cdot 1000 = 16\ 000\]
\[16\ 000\ :1000 = 16\]
\[50 \cdot 10 = 500\]
\[500\ :10 = 50\]
\[60 \cdot 30 = 1800\]
\[1800\ :30 = 60\]
\[80 \cdot 700 = 56\ 000\]
\[56\ 000\ :700 = 80\]
\[\boxed{\mathbf{3.}}\]
\[\textbf{а)}\ 1815 + 70\ 859 + 42 + 487\ 617 =\]
\[= 560\ 333\]
\[\textbf{б)}\ 9\ 205\ 102 - (400\ 000 - 124) =\]
\[= 8\ 805\ 226\]
\[\boxed{\mathbf{4.}}\]
\[\textbf{а)}\ a - a\ :5\ (л) - объем\ ведра\ \]
\[больше\ объема\ банки.\]
\[\textbf{б)}\ c\ :(b\ :8)\ билетов - можно\ \]
\[купить.\]
\[\boxed{\mathbf{5.}}\]
\[\textbf{а)}\]
\[\textbf{б)}\]
\[с)\ \]