# Combination spacing

I need to show the multiplication of two combinations.

Code:

$_4\rm C_2\times_7\rm C_2$


Output:

As you can see, the spacing is strange and hard to read (the '7' is far to the left). How can I fix this? I will be needing to do this very frequently.

• The spacing around the 7 is incorrect as you're setting it as a subscript to \times. – Werner May 11 '16 at 23:29

If you need it frequently, then you need to create a macro for it. It'll make life easier and more consistent!

\documentclass{article}

\usepackage{amsmath}

\newcommand{\comb}[2]{{}_{#1}\mathrm{C}_{#2}}

\begin{document}

$\comb{4}{2} \times \comb{7}{2} = \binom{4}{2} \times \binom{7}{2}$

\end{document}