Multicols and row spacing

I am having trouble with spacing in using multicols. I am trying to give my students enough space to answer each part. However, each part does not line up. I am wondering if there is a single command I can give each time so the rows are automatically spacing a certain distance.

I am new to this site.. Here is a MWE

\documentclass[12pt]{exam}
\usepackage{multicol}
\usepackage{amsfonts}
\usepackage{amssymb}

\usepackage{amsmath}

\begin{document}

\begin{questions}
\question Use the power rule to differentiate
\begin{multicols}{2}
\begin{parts}
\part $\dfrac{1}{x^3}$
\vspace{1.5in}

\part $x^{\frac{1}{2}}$
\vspace{1.5in}
\part $\dfrac{1}{\sqrt{x}}$
\vspace{1.5in}
\part   $y=x\sqrt{15}$
\vspace{1.5in}
\part $3x^4+8x^{10}$
\vspace{1.5in}
\part $5x^4(2-x^3)$
\vspace{1.5in}
\part $(3x^2+5)(x-1)$
\vspace{1.5in}
\part $50x^5+\dfrac{3}{x}-7x^-\frac{5}{3}$
\vspace{1.5in}
\end{parts}
\end{multicols}
\end{questions}
\end{document}

As you can see there is a problem with e and f being out of alignment.

Thanks for any help.

Nick

• welcome to tex.sx, note you can use the {} button to format code sections (see my edit) – David Carlisle Oct 3 '13 at 12:34 You can adjust the height and depth of the rule to be large enough to cover all your examples. Examples larger than that will again push you off the alignment. Change 1pt to 0pt to make the strut invisible.

\documentclass[12pt]{exam}
\usepackage{multicol}
\usepackage{amsfonts}
\usepackage{amssymb}

\usepackage{amsmath}

\def\x{\rule[-.5in]{1pt}{1in}}
\begin{document}

\begin{questions}
\question Use the power rule to differentiate
\begin{multicols}{2}
\begin{parts}
\part\x $\dfrac{1}{x^3}$
\vspace{.5in}

\part\x $x^{\frac{1}{2}}$
\vspace{.5in}
\part\x $\dfrac{1}{\sqrt{x}}$
\vspace{.5in}
\part\x   $y=x\sqrt{15}$
\vspace{.5in}
\part\x $3x^4+8x^{10}$
\vspace{.5in}
\part\x $5x^4(2-x^3)$
\vspace{.5in}
\part\x $(3x^2+5)(x-1)$
\vspace{.5in}
\part\x $50x^5+\dfrac{3}{x}-7x^-\frac{5}{3}$
\vspace{.5in}
\end{parts}
\end{multicols}
\end{questions}
\end{document}