\[\boxed{\text{1143\ (1143).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ 81 \cdot 3^{2} = 3^{4} \cdot 3^{2} = 3^{6} = 729\]
\[2)\ 4^{3} \cdot 8^{2} = \left( 2^{2} \right)^{3} \cdot \left( 2^{3} \right)^{2} =\]
\[= 2^{6} \cdot 2^{6} = 2^{12} = 4096\]
\[3)\ 100^{2} \cdot 1000^{3} =\]
\[= \left( 10^{2} \right)^{2} \cdot \left( 10^{3} \right)^{3} = 10^{4} \cdot 10^{9} =\]
\[= 10^{13} = 10\ 000\ 000\ 000\ 000\ \]