documentclass[dvipdfmx]{article}

% packages
usepackage{pgf}
usepackage{tikz}

% libraries for tikz
usetikzlibrary{fpu}

begin{document}

    pgfkeys{/pgf/fpu=true, pgf/fpu/output format=fixed}
    pgfmathsetmacro{¥Gu}{6.67*10^(-11)}
    pgfkeys{/pgf/fpu=false}
    pgfmathsetmacro{¥Mc}{5.0*random(10,14)}

end{document}