# Split equation into multiple lines

I am trying to split a long equation into lines as explained in one of the answers here using multline (amsmath package:

\begin{multline}
m(X)=1.00 \cdot 0.94 \cdot 1.30 \cdot 1.30 \cdot 1.21 \cdot 1.00 \cdot 1.07 \cdot 1.00 & 1.29 \cdot 0.86 \cdot 1.00 \cdot 0.95 \cdot 1.00 \cdot 0.91 \cdot 1.23 = 2.4262
\end{multline}


However when compiling I am getting an error on the last line saying:

Extra alignment tab has been changed to \cr.

You have written too many alignment tabs in a table, causing one of them to be turned into a line break. Make sure you have specified the correct number of columns in your table.

I can't figure out what's wrong. Also, a magic number (2.1) is being displayed right after the last term of the equation.

multline doesn't use any alignment points, indicated by &, only linebreaks, indicated by \\.

Replace the & in your code by \cdot{} \\. The \cdot was missing, the {} is to get proper spacing.

About the number, I don't know why you say "magic". by default multline is a numbered equation, if you don't want numbering use multline*.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
Numbered:
\begin{multline}
m(X)=1.00 \cdot 0.94 \cdot 1.30 \cdot 1.30 \cdot 1.21 \cdot 1.00 \cdot 1.07 \cdot 1.00 \cdot{} \\ 1.29 \cdot 0.86 \cdot 1.00 \cdot 0.95 \cdot 1.00 \cdot 0.91 \cdot 1.23 = 2.4262
\end{multline}
Or an unnumbered version:
\begin{multline*}
m(X)=1.00 \cdot 0.94 \cdot 1.30 \cdot 1.30 \cdot 1.21 \cdot 1.00 \cdot 1.07 \cdot 1.00 \cdot{} \\ 1.29 \cdot 0.86 \cdot 1.00 \cdot 0.95 \cdot 1.00 \cdot 0.91 \cdot 1.23 = 2.4262
\end{multline*}
\end{document}