The answers on how to spread table columns evenly under a multicolumn seem to suggest that this is not possible, e.g. https://tex.stackexchange.com/a/60604/36836. It seems hard to believe that LaTeX has this restriction.
Here is an example showing the basic problem of spreading columns evenly:
\documentclass{article}
\usepackage{booktabs}
\begin{document}
\begin{tabular}{cccc}
\toprule
& \multicolumn{3}{c}{some longer text here}\\
\cmidrule{2-4}
& 1 & 2 & 3\\
\midrule
some text here & A & B & C \\
\bottomrule
\end{tabular}
\end{document}
The last column, 3, take more space than the other columns.


\divide\dimen0 by 3\\works---but now how to insert text in the first row which remains blank – js bibra Nov 11 '19 at 14:38