\[\boxed{\mathbf{3.49}}\]
\[\textbf{а)}\ 60\ м = 6000\ см\]
\[2,4\ :6000 = \frac{24}{60000} = \frac{4}{10000} =\]
\[= 0,0004.\]
\[\textbf{б)}\ 10\ т = 10\ 000\ кг\]
\[10\ 000\ :250 = 40.\]
\[\textbf{в)}\ 1\ мин = 60\ с\]
\[60\ :12 = 5.\]
\[\textbf{г)}\ 2\ м^{3} = 2\ 000\ 000\ см^{3}\]
\[600\ :2\ 000\ 000 = \frac{6}{20000} =\]
\[= \frac{3}{10000} = 0,0003.\]