Have one centred equation number in the flalign enviroment

I want to use the flalign so I can have left aligned text in-between equations. For example

\begin{flalign}
&& f &= ma&\\
\text{Which we may express as} \\
&& f &= m \frac{dv}{dt}
\end{flalign}


However this gives an equation number for every line, including the \text{...}.

How can I have one equation number that appears centered for the rendered result, as with any other equation number.

• One possible solution is \nonumber on the lines one doesn't wish to see an equation number.
– Q.P.
Aug 24 '20 at 17:52
• This question might help. Aug 24 '20 at 18:17
• Will your readers understand what the number at the level of the textual insertion refers to? Aug 24 '20 at 21:19
• I sure hope so!
– Q.P.
Aug 24 '20 at 21:33

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{flalign}
&& f &= ma&             \notag  \\
\text{Which we may express as}      \\
&& f &= m \frac{dv}{dt} \notag
\end{flalign}

\bigskip\noindent%
You may consider the following solution:
\begin{subequations}\label{eq:sys}
\begin{align}
f &= ma                             \\
\intertext{Which we may express as}
f &= m \frac{dv}{dt}
\end{align}
\end{subequations}
\end{document}


• Nice solution, is there a way to keep the equation centred on the page, while keeping the in-equation text left justified?
– Q.P.
Aug 24 '20 at 20:05
• @Q.P., the second example provide this, Yes, it hasn't common equation number on the vertical middle, however it is replaced by two (to my opinion) more meaningful equation sub numbering. Aug 24 '20 at 20:26