# Standard form in TeX?

How do I write x10 to the power of something within an equation?

At the moment I'm using y \times 10^x, but it gets slightly confusing if I have a long line of numbers that I'm multiplying together.

This the equation I have now:

g = \frac{6.67 \times 10^{-11} \times 6 \times 10^{24}}{6400010^2}


Which produces the output:

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Welcome to TeX.sx! May you expand your question showing an example of what you have to do? –  egreg Dec 11 '12 at 21:34
How does it look with parentheses: (a x 10^b) x (c x 10^d)? –  krlmlr Dec 11 '12 at 21:38
Yes that does improve the clarity, but it's a workaround not a fix. :( –  Todd Davies Dec 11 '12 at 21:46

If you need to typeset actual numbers (and not symbols as in your example), you could use the \num macro provided by siunitx. It allows you to type \num{2e3} to output , both in math and in text mode.

When multiplying numbers in exponential form, you could reduce the spacing within the numbers, using tight-spacing=true:

\documentclass{article}
\usepackage{siunitx}

\begin{document}

\sisetup{tight-spacing=true}
$g = \frac{\num{6.67e-11} \times \num{6e24}}{6400010^2}$
\end{document}

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@ToddDavies: Ah, okay, I think now I understand your problem. The repeated use of \times is confusing for the reader. Hm... –  Jake Dec 11 '12 at 21:40
This is the cleanest solution, it appeals to the programmer in me! Thanks Jack! –  Todd Davies Dec 11 '12 at 21:51
I think I would write the middle \times as a \cdot. –  Manuel Dec 11 '12 at 21:57
@Manuel: Mathematically, all the operations are just multiplications, so I don't think it's a good idea to use different symbols for the same thing. I think the choice of whether to use a dot or a cross for multiplication of single numbers is largely a cultural one (en.wikipedia.org/wiki/Multiplication#Notation_and_terminology), but one should be consistent. –  Jake Dec 11 '12 at 22:02
@Manuel: I think in cultures where a comma is used as a decimal separator, a dot is frequently used for multiplications, including in scientific notation (e.g. in German, see de.wikipedia.org/wiki/Wissenschaftliche_Notation). In English, this is avoided because of the danger of confusion with the period decimal separator, so a cross is used for everything (except scalar products of matrices, of course, but that's a different matter). –  Jake Dec 11 '12 at 22:25
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I know many will disagree with the following but nonetheless this what I used to use:

\newcommand{\sn}[2]{\ensuremath{{#1}\times 10^{#2}}}


And I use it like this: \sn{y}{x}. Here is an example:

\documentclass{article}
\usepackage[dvipsnames]{xcolor}
\usepackage{amsmath}

\newcommand{\sn}[2]{\ensuremath{{#1}\times 10^{#2}}}

\begin{document}
\begin{align*}
(\sn{2.25}{\textcolor{Cerulean}{4}})(\sn{7.5}{\textcolor{OrangeRed}{6}})    &= \sn{(2.25)(7.5)}{\textcolor{Cerulean}{4}+\textcolor{OrangeRed}{6}}\\
&= \sn{16.875}{10}\\
&= \sn{1.6875}{11}\\
&= \sn{1.7}{11} \quad(\text{2 s.f.})
\end{align*}
\end{document}

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