\[\boxed{\mathbf{253.}}\]
\[\textbf{а)}\ 1 - \left( \frac{1}{9} + \frac{1}{3} + \frac{1}{6} + \frac{1}{4} + \frac{1}{8} \right) =\]
\[= 1 - \frac{8 + 24 + 12 + 18 + 9}{72} =\]
\[= 1 - \frac{71}{72} = \frac{1}{72}.\]
\[= 1 - (0,1 + 0,2 + 0,3 + 0,36) =\]
\[= 1 - 0,96 = 0,04.\]