ed ecco il risultato finale
non è bello ma..
`
% !TEX TS-program = pdflatex
% !TEX encoding = UTF-8 Unicode
\documentclass{article}
\usepackage{array}
\newcolumntype{C}[1]{>{\centering}p{#1}}
% oppure senza argomento
% \newcolumntype{C}{>{\centering}p{20mm}}
\newcolumntype{M}[1]{>{\centering\rule[-3mm]{0pt}{8mm}}m{#1}}
\newcolumntype{N}[1]{>{\centering\rule[-1mm]{0pt}{2mm}}m{#1}}
\begin{document}
%\begin{tabular}{@{}|M{6mm}|*5{M{22.6mm}|}@{}}
% oppure
%\begin{tabular}{*5C}
\begin{tabular}{l}
%\setlength{\arrayrulewidth}{2pt}
\begin{tabular}{@{}|N{6mm}|N{18mm}|*2{N{24.6mm}|}*2{N{10.6mm}|} }%{|C{6mm}|*5{C{22.6mm}|}@{}}
\hline
&A &B &C &D&E\tabularnewline
\end{tabular}\\
\begin{tabular}{@{}|M{6mm}|M{18mm}|*2{M{24.6mm}|}*2{M{10.6mm}|} @{}}
% oppure
\hline
1& $x_i$ & $n_i$ & $x_i\cdot n_i$ &&\tabularnewline
\hline
2& 6 & 8 & =A2*B2 &M=&=C6/B6 \tabularnewline
\hline
3& 3 & 6 & =A3*B3 && \tabularnewline
\hline
4&4 & 5 & =A4*B4 && \tabularnewline
\hline
5&5 & 3 & =A5*B5 && \tabularnewline
\hline
6&Totali & =somma(B2:B5) & =somma(B2:B5) && \tabularnewline
\hline
\end{tabular}\\
\end{tabular}
\end{document}
`
claudio