> 欄だけ残すのはちょっと考え中です。

No.7646 を見逃したのでピントはずれの発言かもしれません。
次のソースは、現在私の使用しているひな形です。
プリアンブル部の emathAe の入り換えのみで、
全体が切り替わりレイアウトを崩さないのがプチ自慢です。

\documentclass[b4j]{jarticle}%
\usepackage[papersize,notMy]{emathP}%
%\usepackage[maskAnstrue]{emathAe}%
\usepackage[maskAnsfalse]{emathAe}%
\usepackage{hako}%
\usepackage{emathMw}%
\pagestyle{empty}%

\columnseprule=0.1mm%

%%%%%%%%%%%%%%%%% 解答の色を定義 %%%%%%%%%%%%%%%%%%%
%\def\AnsCol{black}%
\def\AnsCol{red}%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%% ここは触らない %%%%%%%%%%%
\ifmaskAns
\hakokaisyotai{\color{white}\ensuremath}
\else
\hakokaisyotai{\color{\AnsCol}\ensuremath}
\fi
\def\KaitouTTL{\color{\AnsCol}\relax}%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\renewcommand{\labelenumi}{{\preitem\large\fbox{\protect\makebox[1.2em][c]{\bfseries\ {\arabic{enumi}}\ }}}}%
\renewcommand{\labelenumii}{\preitem(\arabic{enumii})\ }%
\renewcommand{\labelenumiii}{{\preitem{\small(\protect\makebox[0.8em][c]{\roman{enumiii}})}}}%
\let\theenumi\labelenumi%
\let\theenumii\labelenumii%
\let\theenumiii\labelenumiii%

\begin{document}%
\twocolumn[%
{\Large\textbf{タイトル}}%
\qquad%
{\tt(YYYY/MM/DD)}%
\hfill%
\underline{\ 2年\qquad{}組\qquad{}番\ 氏名\hspace*{16zw}\ }\ %
\vspace*{3mm}%

]%

\enumLmargin{0.5zw}%
次の \karaHako に適当な数または符号を入れよ。%
答は解答欄に記入せよ。%

\begin{enumerate}%
\hakosyokika%
\openHakoKaiFile%
\centermodetrue%
\item %
\begin{enumerate}%
\item %
\begin{mawarikomi}{}%
{%
\begin{zahyou*}[ul=5mm,Yohaku=0.5\unitlength](-3,3)(-2,2)%
\Takakkei{\LB\RB\RT\LT}%
\Put{(0,0)}[c]{説明図}%
\end{zahyou*}%
}%
\repeatstr{問題文\relax}{20}%

$\text{分数}=\Bunsuu{\Hako'13'}{\Hako'2'}$, %

$\text{相似比}=\Hako'2':\Hako'1'$
\end{mawarikomi}

\begin{Kaitou}%
\medskip%
\repeatstr{解説文\relax}{20}%
\end{Kaitou}%


\vfill%
\item %

\begin{mawarikomi}{}%
{%
\begin{zahyou*}[ul=5mm,Yohaku=0.5\unitlength](-3,3)(-2,2)%
\Takakkei{\LB\RB\RT\LT}%
\Put{(0,0)}[c]{説明図}%
\end{zahyou*}%
}%
\repeatstr{問題文\relax}{20}%

$\text{長整数}=\Hako'12345'$, %

$\text{負の数}=\Hako'-23'$%
\end{mawarikomi}%

\begin{Kaitou}%
\medskip%
\repeatstr{解説文\relax}{20}%
\end{Kaitou}%

\vfill%
\end{enumerate}%

\closeHakoKaiFile%

\noindent{}【解答欄】%

\HakoKaiKata{t}%
\HakoKaiSityuu[1zh]{1.5zh}%
\inputHakoKaiFile%
\newpage%
\item %
\repeatstr{問題文\relax}{20}%
\end{enumerate}%
\end{document}%

▼関連発言
│
└◆7644:hakoで解答の非表示 [take] 10/23 16:10
　├◆7645:Re:hakoで解答の非表示 [boo] 10/23 17:35
　├◆7646:--- [---] 10/23 17:48
　│├◆7647:Re[2]:hakoで解答の非表示 [boo] 10/23 18:09
　││└◆7648:Re[3]:hakoで解答の非表示 [take] 10/23 18:18
　│└◆7649:Re:--- [石原　守] 10/23 19:05
　│　└◆7651:Re[2]:レイアウトを崩さず切り替える [田中徹] 10/24 22:10
　│　　└◆7652:Re[3]:レイアウトを崩さず切り替える [石原　守] 10/25 05:43
　└◆7653:\usepackage[maskAnstrue]{emathAe} にご注意 [tDB] 10/25 11:14
　　└◆7654:　　訂正 [tDB] 10/25 14:07<-last