[tex]\bf \begin{array}{|ll|ll} \cline{1-2} bridge&\stackrel{tons}{materials}\\ \cline{1-2} concrete&1,000\\ \textit{steel structure} & 400\\ \textit{glass and granite}&200\\ \cline{1-2} \end{array}\qquad \qquad \stackrel{~\hfill \textit{total weight}}{1000+400+200=1600} \\\\[-0.35em] ~\dotfill[/tex]
[tex]\bf \cfrac{\stackrel{\textit{steel structure}}{400}}{\underset{\textit{total weight}}{1600}}\implies \stackrel{\textit{simplified}}{\cfrac{1}{4}}~\hfill \cfrac{\stackrel{\textit{glass and granite}}{200}}{\underset{\textit{total weight}}{1600}}\implies \stackrel{\textit{simplified}}{\cfrac{1}{8}}[/tex]