%@Auteur: d'après IREM Strasbourg\par
\vspace{1cm}\par
\begin{minipage}{0.4\linewidth}
\rnode{A}{20}\kern7cm\rnode{B}{\raisebox{6pt}{}}\ldots
%haut
\ncbar[angleA=90,nodesep=3mm,offsetB=2mm]{->}{A}{B}
\ncput*{$\times\ldots$}
%milieu
\ncline[linecolor=white,nodesep=3mm]{-}{A}{B}
\ncput*{\rnode{D}{\ldots}}
\ncline[nodesepA=3mm,nodesepB=3mm]{->}{A}{D}
\ncput*{$\times10$}
\ncline[nodesep=3mm]{->}{D}{B}
\ncput*{$\div4$}
%bas
\ncbar[angleA=-90,nodesep=3mm,linecolor=white]{->}{A}{B}
\ncput*{\rnode{C}{\ldots}}
\ncangles[angleA=-90,angleB=180,nodesep=3mm]{->}{A}{C}
\ncput*{$\div\ldots$}
\ncangles[angleB=0,angleA=-90,nodesep=3mm,offsetA=2mm]{<-}{B}{C}
\ncput*{$\times\ldots$}
\end{minipage}
\hfill
%n2
\begin{minipage}{0.4\linewidth}
\rnode{A}{20}\kern7cm\rnode{B}{\raisebox{6pt}{}}\ldots
%haut
\ncbar[angleA=90,nodesep=3mm,offsetB=2mm]{->}{A}{B}
\ncput*{$\times\ldots$}
%milieu
\ncline[linecolor=white,nodesep=3mm]{-}{A}{B}
\ncput*{\rnode{D}{\ldots}}
\ncline[nodesepA=3mm,nodesepB=3mm]{->}{A}{D}
\ncput*{$\times2$}
\ncline[nodesep=3mm]{->}{D}{B}
\ncput*{$\div5$}
%bas
\ncbar[angleA=-90,nodesep=3mm,linecolor=white]{->}{A}{B}
\ncput*{\rnode{C}{\ldots}}
\ncangles[angleA=-90,angleB=180,nodesep=3mm]{->}{A}{C}
\ncput*{$\div\ldots$}
\ncangles[angleB=0,angleA=-90,nodesep=3mm,offsetA=2mm]{<-}{B}{C}
\ncput*{$\times\ldots$}
\end{minipage}
\par\vspace*{1cm}\par
Complète les schémas de calculs ci-dessus par des nombres entiers ou décimaux.