考试类别：矩阵内\填写答案行

Question

我想制作一张工作表，让学生在\fillin[]答案行内写矩阵。从以下示例中可以看出，\fillin[]似乎在写入单个数字系数时工作正常，但在矩阵方面存在问题。我收到错误：“缺少插入的 $。”

以下是 MWE：

\documentclass[openright, notitlepage]{book}
\usepackage{exam}
\addpoints
\printanswers
\usepackage[utf8]{inputenc}
\usepackage[margin=.75 in]{geometry}
\usepackage{amsmath,amsfonts,amssymb,amsthm,color,srcltx,bm,cancel}
\setlength\fillinlinelength{1cm}
\setlength\answerclearance{1.25ex}

\begin{document}
\section{Matrix Multiplication Practice}
\begin{questions}
\question
Please fill in the blanks:
\begin{equation*}
\begin{bmatrix}
a & b & c & d \\
e & f & g & h \\
i & j & k & l
\end{bmatrix}
\begin{bmatrix}2 \\ 3 \\ 4 \\ 5
\end{bmatrix}
= 
\fillin[2]
\begin{bmatrix} a \\ e \\ i  \end{bmatrix}
+
\fillin[3]
\begin{bmatrix} b \\ f \\ j  \end{bmatrix}
+
\fillin[4]
\begin{bmatrix} c \\ g \\ k  \end{bmatrix}
+
\fillin[5]
\begin{bmatrix} d \\ h \\ l  \end{bmatrix}
\end{equation*}


\question
\setlength\answerclearance{7ex}
Please fill in the blanks:
\begin{equation*}
\begin{bmatrix}
h & y & w & s \\
e & o & a & u \\
y & u & t & p
\end{bmatrix}
\begin{bmatrix} 3 \\ 4 \\ 5 \\ 6 \end{bmatrix}
= 
3
\fillin[\begin{bmatrix}h \\e \\y \end{bmatrix}]
+
4
\fillin[\begin{bmatrix}y \\o \\u \end{bmatrix}]
+
5
\fillin[\begin{bmatrix}w \\a \\t \end{bmatrix}]
+
6
\fillin[\begin{bmatrix}s \\u \\p \end{bmatrix}]
\end{equation*}
\end{questions}
\end{document}

尽管存在错误，但输出看起来还不错（我只是希望我不必手动调整\fillin[]使用的答案间隙\setlength\answerclearance{7ex}，这需要根据向量的高度进行一些猜测。）

知道如何修复该Missing $ inserted错误吗？

Answer 1

重新定义以将基线以下的答案的深度\filling添加到本地。\answerclearance

注意使用examclass 而不是book。

\documentclass[openright, notitlepage]{exam} % changed <<<<<<<<<<<<<<
%\usepackage{exam} %% does not work
\addpoints
\printanswers
\usepackage[utf8]{inputenc}
\usepackage[margin=.75 in]{geometry}
\usepackage{amsmath,amsfonts,amssymb,amsthm,color,srcltx,bm,cancel}
\setlength\fillinlinelength{1cm}
\setlength\answerclearance{1.25ex}

% *************************************** added <<<<<<<<<<<<<<<<
\usepackage{xpatch} 
\newsavebox{\answerholder}
\newlength{\Danswerholder}  
\newcounter{applied}
        
\makeatletter
\xpatchcmd{\questions}
{\addtocounter{numquestions}{1}}
{\addtocounter{numquestions}{1}\setcounter{applied}{0}}
{}{}

\renewcommand\fillin[1][{}]{%
\savebox{\answerholder}{#1}
\setlength{\Danswerholder}{\the\dp\answerholder}
\ifdim\Danswerholder>\the\fontchardp\font`g\ifnum \value{applied}=0%
 \addtolength\answerclearance\Danswerholder \stepcounter{applied}
\fi\fi%         
\def\fillin@ans{#1}\fillin@relay                
}% 
\makeatother        
%*************************************** 

\begin{document}
        
    \section{Matrix Multiplication Practice}
    \begin{questions}
        \question
        Please fill in the blanks:
        \begin{equation*}
            \begin{bmatrix}
                a & b & c & d \\
                e & f & g & h \\
                i & j & k & l
            \end{bmatrix}
            \begin{bmatrix}2 \\ 3 \\ 4 \\ 5
            \end{bmatrix}
            = 
            \fillin[2]          
            \begin{bmatrix} a \\ e \\ i  \end{bmatrix}
            +
            \fillin[3]
            \begin{bmatrix} b \\ f \\ j  \end{bmatrix}
            +
            \fillin[4]
            \begin{bmatrix} c \\ g \\ k  \end{bmatrix}
            +
            \fillin[5]
            \begin{bmatrix} d \\ h \\ l  \end{bmatrix}
        \end{equation*}     
        
        \question               
        Please fill in the blanks: 
        \begin{equation*}
            \begin{bmatrix}
                h & y & w & s \\
                e & o & a & u \\
                y & u & t & p
            \end{bmatrix}
            \begin{bmatrix} 3 \\ 4 \\ 5 \\ 6 \end{bmatrix}
            = 
            3
            \fillin[$\begin{bmatrix}h \\e \\y \\q  \\w \end{bmatrix}$]  
            +
            4
            \fillin[$\begin{bmatrix}y \\o \\u \\q  \\w\end{bmatrix}$]
            +
            5
            \fillin[$\begin{bmatrix}w \\a \\t \\q  \\w\end{bmatrix}$]
            +
            6
            \fillin[$\begin{bmatrix}s \\u \\p \\q  \\w\end{bmatrix}$]               
        \end{equation*}     
    
        
        \question
        Please fill in the blanks: 
        
        \begin{equation*}
            \begin{bmatrix}
                h & y & w & s \\            
                y & u & t & p
            \end{bmatrix}
            \begin{bmatrix} 3 \\ 4 \\ 5 \\ 6 \end{bmatrix}
            = 
            3
            \fillin[$\begin{bmatrix}h  \\y \end{bmatrix}$]  
            +
            4
            \fillin[$\begin{bmatrix}y  \\u \end{bmatrix}$]
            +
            5
            \fillin[$\begin{bmatrix}w  \\t \end{bmatrix}$]
            +
            6
            \fillin[$\begin{bmatrix}s \\p \end{bmatrix}$]               
        \end{equation*} 
    
    \end{questions}
\end{document}