How to build a three column table with tabularx

Question

I'm attempting to build a simple three column table using tabularx, but I must be misunderstanding some aspect of the code because my table is visibly not working out.

My goal is to have three equal column widths but no matter what I try the lines do not seem to match up. (I will also need to work on centering the text and keeping 'information' as a single word, but those problems are comparatively minor!)

My code for creating the table is below.

    \caption{Common Curriculum}
    \centering
    \begin{tabularx}{0.9\linewidth}[ht]{||p{0.3\linewidth} | p{0.3\linewidth} | p{0.3\linewidth}||} 
        \hline
        Physical Concepts & Mathematical Skills and Notation & Application in Quantum Information  \\  
        \hline\hline
        1 & 6 & 87837  \\ 
        \hline
        2 & 7 & 78  \\
        \hline
        3 & 545 & 778  \\
        \hline
        4 & 545 & 18744  \\
        \hline
        5 & 88 & 788  \\ 
        \hline
    \end{tabularx}
    \label{tab:CommonCurr}.
\end{table}

I've tried using {\textwidth} instead of {0.9\linewidth}. I've also tried using thirds of the textwidth, but I assumed the problem with that idea was due to rounding as my horizontal lines then extended beyond the table giving me an opposite problem.

Any help would be appreciated!

Answer 1

I wonder if may liked the following table form:

Az writing of the above "professional looking" table are used the tabularraypackage with libraries (which load packages of the same names) and a bit narrower table:

\documentclass{article}
\usepackage[skip=0.33\baselineskip]{caption}
\usepackage{tabularray}
\UseTblrLibrary{booktabs, siunitx}

\begin{document}
    \begin{table}[ht]
\caption{Common Curriculum}
\label{tab:CommonCurr}
    \centering
\begin{tblr}{width=0.75\linewidth,
             colspec = {X[c] 
                        X[c, si={table-format=3.0}] 
                        X[c, si={table-format=5.0}]},
             row{even}  = {belowsep=-2pt},
             row{1} = {guard, c}
             }
    \toprule
{Physical\\ Concepts}
    & Mathematical Skills and Notation 
        & Application in Quantum Information  \\
    \midrule
1   & 6     & 87837     \\
2   & 7     & 78        \\
3   & 545   & 778       \\
4   & 545   & 18744     \\
5   & 88    & 788       \\
    \bottomrule
\end{tblr}
    \end{table}
\end{document}

However, if you more prefer each cells in "jail" of horizontal and vertical lines as you show in your question, than MWE is:

\documentclass{article}
\usepackage[skip=0.33\baselineskip]{caption}
\usepackage{tabularray}
\UseTblrLibrary{siunitx}

\begin{document}
    \begin{table}[ht]
\caption{Common Curriculum}
\label{tab:CommonCurr}
    \centering
\begin{tblr}{width=0.75\linewidth,
             hlines, vlines,
             colspec = {X[c] 
                        X[c, si={table-format=3.0}] 
                        X[c, si={table-format=5.0}]},
             row{1} = {guard, c}
             }
{Physical\\ Concepts}
    & Mathematical Skills and Notation 
        & Application in Quantum Information  \\
1   & 6     & 87837     \\
2   & 7     & 78        \\
3   & 545   & 778       \\
4   & 545   & 18744     \\
5   & 88    & 788       \\
\end{tblr}
    \end{table}
\end{document}

and table is than: