\[q = 0,1;\]
\[S = \frac{0,04}{1 - 0,1} = \frac{0,04}{0,9} = \frac{4}{90} = \frac{2}{45};\]
\[\frac{6}{10} + \frac{2}{45} = \frac{54 + 4}{90} = \frac{58}{90} = \frac{29}{46};\]
\[0,6444\ldots = \frac{29}{45}.\]