\[\boxed{\mathbf{748}\mathbf{.}}\]
\[T = T_{0} + \left( T_{1} - T_{0} \right) \cdot a^{t}\]
\[290 = 20 + (320 - 20) \cdot a^{10}\]
\[300 \cdot a^{10} = 270\ \ \ |\ 300\]
\[a^{10} = \frac{9}{10}\]
\[a = \sqrt[10]{\frac{9}{10}}\]
\[T = 20 + 300 \cdot a^{10}\]
\[T(30) = 20 + 300 \cdot \left( \sqrt[10]{\frac{9}{10}} \right)^{30} =\]
\[= 20 + 300 \cdot \left( \frac{9}{10} \right)^{3} =\]
\[= 20 + \frac{300 \cdot 729}{1000} =\]
\[= 20 + 218,7 = 238,7.\]
\[Ответ:238,7{^\circ}С - температура\]
\[\ заготовки.\]