Consider the following macro:

```
\newcommand{\sxfigure}[4]{
\includegraphics[width=#1*#3 cm, height=#2*#3 cm]{#4}
}

```

`#1` and `#2` is some value to determine the width and height of the figure, `#3` is to control the zoom ratio. However, the above code doesn't work. Could someone provide a solution? I have tried the following, still not work. Could some point out the mistake?

```
\usepackage{pgf}
\newcommand{\sxmultiply}[2]{\pgfmathparse{#1*#2}\pgfmathresult}
\newcommand{\sxfigure}[5]{
\begin{figure}
\begin{center}
\includegraphics[width=$\sxmultiply{#3}{#5}$ cm, height=$\sxmultiply{#4}{#5}$ cm]{#1}
\end{center}
\caption{#2}
\end{figure}
}

```