Underline for an answer

Question

In Japan, it is very common to underline an answer in a math exam sheet with this:

(Usual underline plus two slashes at the end.) Can I find a macro for this in some package? If not, do I have to create it with TikZ?

I've tried \underline{45\tiny$_{\!/\!\!/}$}, but the result was not what I desired.

Answer 1

With TikZ you can create a macro for this purpose. For example:

\documentclass{article}
\usepackage   {tikz}

\newcommand{\mysol}[1]
{% <-- We don't need a space here
  \begin{tikzpicture}[baseline=(a.base),line width=0.1ex]
    \node[inner sep=0] (a) at (0,0) {$#1$};
    \draw (a.south west) -- ([xshift=1.5ex]a.south east);
    \foreach\i in {0,0.5}
      \draw ([xshift=\i ex,yshift=-0.5ex]a.south east) --++ (1ex,1ex);
  \end{tikzpicture}% <-- We don't need a space here either
}

\begin{document}
\textbf{Problem.} The bottom of a ladder must be placed $3$ feet from a wall.  The ladder is $12$ feet long.  How far above the ground does the ladder touch the wall?
\bigskip

\textbf{Solution.} By the Pythagorean Theorem,
\[a^2=b^2+c^2\Longrightarrow b=\sqrt{a^2-b^2}=\sqrt{12^2-3^2}=\sqrt{135}=\mysol{3\sqrt{15}}.\]
So the ladder touches the wall \mysol{3\sqrt{15}} feet above the ground.
\end{document}

Note that if the solution will not be in math mode you must remove the $...$ inside the node in the macro.

Answer 2

I think you don't need TikZ for this:

\documentclass{article}
\usepackage{amsmath}
\newlength{\mylen}
\newlength{\mydepth}

\newcommand{\myunder}[1]{\settowidth{\mylen}{\tiny${\!/\!\!/}$}%
    \settodepth{\mydepth}{#1}%
    \addtolength{\mydepth}{.6ex}%
    \underline{#1\hspace{\mylen}}\hspace{-\mylen}\raisebox{-\mydepth}{\tiny${\!/\!\!/}$}}
\begin{document}
Ordinary answer: \myunder{45}

Answer with \verb|\cfrac|: \myunder{$\cfrac{44}{45}$}
\end{document}

Answer 3

You could do this way:

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}

\newcommand{\solution}[1]{%
  % store the text so we can measure it
  % the underline will always be below the baseline
  \sbox0{\underline{#1}}%
  % measure the double slash
  \sbox2{\raisebox{\depth}{\solutionsymbol}}%
  % do the job (assuming the underline is 0.4pt thick)
  \dimen0=\dimexpr\dp0+\ht2/2-\fontdimen8\textfont3\relax
  \underline{#1\!\raisebox{-\dimen0}[0pt][0pt]{\usebox{2}}}%
  % add the depth we smashed out
  \vphantom{\raisebox{-\dimen0}{\usebox{2}}}%
}
\newcommand{\solutionsymbol}{\scalebox{1}[0.33333]{/\!\!/}}

\begin{document}

Some text \solution{$45$}

\bigskip

Some text \solution{$\dfrac{1}{2}$}

\end{document}