\[\boxed{\text{6.211.}}\]
\[\textbf{а)}\ 1\ :750 = \frac{1}{750}\ \]
\[(не\ делится\ по\ другому).\]
\[\textbf{б)}\ 0,707\ :35 = 0,0202\ \]
\[\textbf{в)}\ 16\ :5 = 3,2\ \]
\[\textbf{г)}\ 6\ :64 = 0,09375\ \]
\[\textbf{д)}\ 0,01278\ :71 = 0,00018\]
\[\textbf{е)}\ 0,1242\ :69 = 0,0018\]