# missing inserted endgroup

I'm typing this equation

\eta=\frac{82\cdot4\cdot1.44 \textrm{MeV}\cdot10$^-15$\textrm{m}}{2\cdot6.582\cdot 10$^-10$ \textrm{MeV}\cdot\textrm{s}\cdot0.0774\cdot2.998\cdot10$^8$\textrm{ms$^-1$}}


and I'm not able to find the mistake.

• You don't need the additional switch to math-mode for superscipts like $^{10}$. Just use ^{10} or ^{-15}. Note the braces to group the entire thing that needs to go in the superscript. – Werner Feb 22 '14 at 18:17
• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – karlkoeller Feb 22 '14 at 18:46
• Since you haven't accepted a single answer, I don't expect you to do it here, either, but one can hope... – Svend Tveskæg Jan 28 '15 at 4:20

Here is one way of doing it using the siunitx package:

\documentclass{article}

\usepackage[
%  locale = DE,% comma instead of full stop as decimal separator
exponent-product = \cdot,
inter-unit-product = \ensuremath{{}\cdot{}}
]{siunitx}

\begin{document}

$$\eta = \frac{82 \cdot 4 \cdot \SI{1.44}{\MeV} \cdot \SI{e-15}{\m}}% numerator {2 \cdot \SI{6.582e-10}{\MeV\s} \cdot \num{0.0774} \cdot \SI{2.998e8}{\m\per\s}}% denominator$$

\end{document}