# Keep getting an error with the code for this equation!

I've been trying to get this to work, but I keep getting errors saying Paragraph ended before \end was complete. I can't see where the issue is though. Could someone help?

\documentclass[12pt, a4paper]{article}
\usepackage{amsmath}
\usepackage[T1]{fontenc}

\begin{document}

When hydrogen is the fuel used:
\begin{equation*}
U_t=2249\ln \frac{1\times10^{6}{1\times10^6-424.6t}}
\end{equation*}

When kerosene is the fuel used:
\begin{equation*}
U_t=1737\ln \frac{1\times10^{6}{1\times10^6-1022t}}
\end{equation*}

When hydrazine is the fuel used:
\begin{equation*}
U_t=2025\ln \frac{1\times10^{6}{1\times10^6-1004t}}
\end{equation*}

\end{document}

-
You have a problem with \frac, it needs two parameters. And you have one in the code. –  m0nhawk Jan 7 at 18:42
Thank you, I hadn't realized I'd made a mistake with the braces over there. –  TheSarcasticScientist Jan 8 at 2:04

As noted above, there is something wrong with the "Fraction". A fraction is created using the \frac{numerator}{denominator} command. See here for some excellent hints.
When hydrogen is the fuel used: