\[\boxed{\mathbf{3.}\mathbf{37}}\]
\[\textbf{а)}\ 30 \cdot 40 < 33 \cdot 45 < 40 \cdot 50\]
\[Так\ как\ \]
\[30 < 33 < 40;\]
\[40 < 45 < 50.\]
\[Так\ как\ \]
\[400 < 404 < 500;\]
\[700 < 732 < 800.\]
\[\textbf{в)}\ 1500 < 36 \cdot 53 < 2400\]
\[30 \cdot 50 < 36 \cdot 53 < 40 \cdot 60\]
\[Так\ как\ \]
\[30 < 36 < 40;\]
\[50 < 53 < 60.\]
\[\textbf{г)}\ 45\ 000 < 91 \cdot 552 < 59\ 000\]
\[90 \cdot 500 < 91 \cdot 552 < 100 \cdot 590\]
\[Так\ как\ \]
\[90 < 91 < 100;\]
\[500 < 552 < 590.\]