Alignment of material across pages

Question

How would you make two corresponding lists on two different pages so that the corresponding items in the two lists would be at the same absolute height on the two pages? I guess the best way to explain the sort of thing I'm looking for is through an example. One middle school math contest, MATHCOUNTS, does this for their question and answer pages (sometimes). See https://mathcounts.org/Page.aspx?pid=295. Open the 2011 State Competition Sprint Round and 2011 State Competition Answer Key pdfs. You will notice that on the answer key, the answers are spaced so that if a student's completed test and the answer key are lined up side by side, the lines will match up for easy grading.

I don't even know how to begin... thanks.

Answer 1

One possibility would be to put a switch in your document that uses \rlap and \vphantom to make the questions disappear, but leaves a vertical space in their place.

\documentclass{article}
\let\myrlap\relax
\let\myvphantom\relax
\newcommand\questionsoff{\let\myrlap\rlap\let\myvphantom\vphantom}
%
\begin{document}
%\questionsoff  % <--- activate to create answer sheet
\noindent
\myrlap{\myvphantom{\begin{minipage}[t]{0.6\textwidth}%
This is a really hard question, which you are
not going to be able to answer. You may as well go
home now. 
\end{minipage}}\hfill}%
\begin{minipage}[t]{0.2\textwidth}
Answer:
\end{minipage}

\bigskip\noindent
\myrlap{\myvphantom{\begin{minipage}[t]{0.6\textwidth}%
This is another really hard question, which you are
not going to be able to answer. You should have 
given up by now.
\end{minipage}}\hfill}%
\begin{minipage}[t]{0.2\textwidth}
Answer:
\end{minipage}
\end{document}

There's quite a lot of work to do to make this into a workable solution, but it's a start.