Align 5 Equations with \align in 2 columns

I was wondering if it is possible to align equations within an two column environment so they make better use of the space.

I tried this but it did not work:

\documentclass[a4paper]{article}
\usepackage{amsmath,siunitx}
\usepackage{mathtools}
\usepackage{multicol}

\begin{document}

\begin{multicols}{2}
\noindent
\begin{align*}
t_a &= \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} \\
&= \SI{10}{\second}
\\
h_a &= \frac{1}{2} \times \SI{6}{\metre\per\second\squared} \times {\SI{10}{\second}}^2 \\
&= \SI{30}{\metre}
\\
h_v  &=  \SI{300}{\metre} - \SI{30}{\metre} - \SI{30}{\metre} \\
&= \SI{240}{\metre}
\\
t_v  &=  \frac{\SI{240}{\metre}}{\SI{6}{\metre\per\second}} \\
&= \SI{40}{\second}
\\
t_t  &= 2 \times (\SI{10}{\second} + \SI{40}{\second} + \SI{8}{\second}  + \SI{120}{\second}) \\
&= \SI{356}{\second}
\end{align*}
\end{multicols}

\end{document}
• Are you really in a two column environment, or is it just for the sake of saving space for your equations? – Bernard Jul 23 '17 at 17:34
• Can you show what you want like result? – juanuni Jul 23 '17 at 17:40
• Maybe this was misleading. I just want to two column locally to save space. – Redfox87678 Jul 23 '17 at 17:44

The align and alignat environments allow for several alignment columns. For n columns, it will require 2n – 1 ampersands. The syntax is this: each new column (no the first one) is introduced by an ampersand, and inside this column, the alignment point is set by a second ampersand.

I slightly simplified your code (needless to load amsmath if you load mathtools: the latter does it for you, anf you can use abbreviations for units).

\documentclass[a4paper]{article}
\usepackage{siunitx}
\usepackage{mathtools}

\begin{document}

\begin{align*}
t_a & = \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} & h_a & = \frac{1}{2} × \SI{6}{\metre\per\second\squared} × {\SI{10}{s}}² \\
& = \SI{10}{s} & & = \SI{30}{m} \\[1ex]
t_v & = \frac{\SI{240}{m}}{\SI{6}{\metre\per\second}} & h_v & = \SI{300}{m} - \SI{30}{m} - \SI{30}{m} \\
& = \SI{40}{s} & & = \SI{240}{m} \\[1ex]
t_t & = 2 × (\SI{10}{s} + \SI{40}{s} + \SI{8}{s} + \SI{120}{s}) \\
& = \SI{356}{s}
\end{align*}

\end{document}

Update:

To add numbers on the left side to the groups of equations (not referable tags), you can add them by hand, and have different layouts.

With flalign*, the numbers will be at the left margin, but the last equation in the columns will end at the right margin. With align* or alignat*, they wuill be aligned, at some distance on the left of the left column. This distance depends on the contents of the equations for align*, whereas you have full control with alignat*:

\documentclass[a4paper]{article}
\usepackage[showframe]{geometry}
\usepackage{siunitx}
\usepackage{mathtools}

\begin{document}

\begin{flalign*}
& 1) & t_a & = \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} & h_a & = \frac{1}{2} × \SI{6}{\metre\per\second\squared} × {\SI{10}{s}}² \\
& & & = \SI{10}{s} & & = \SI{30}{m} \\[1ex]
& 2) & t_v & = \frac{\SI{240}{m}}{\SI{6}{\metre\per\second}} & h_v & = \SI{300}{m} - \SI{30}{m} - \SI{30}{m} \\
& & & = \SI{40}{s} & & = \SI{240}{m} \\[1ex]
& 3) & t_t & = 2 × (\SI{10}{s} + \SI{40}{s} + \SI{8}{s} + \SI{120}{s}) \\
& & & = \SI{356}{s}
\end{flalign*}

\begin{align*}%{3}
& 1) & t_a & = \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} & h_a & = \frac{1}{2} × \SI{6}{\metre\per\second\squared} × {\SI{10}{s}}² \\
& & & = \SI{10}{s} & & = \SI{30}{m} \\[1ex]
& 2) & t_v & = \frac{\SI{240}{m}}{\SI{6}{\metre\per\second}} & h_v & = \SI{300}{m} - \SI{30}{m} - \SI{30}{m} \\
& & & = \SI{40}{s} & & = \SI{240}{m} \\[1ex]
& 3) & t_t & = 2 × (\SI{10}{s} + \SI{40}{s} + \SI{8}{s} + \SI{120}{s}) \\
& & & = \SI{356}{s}
\end{align*}

\begin{alignat*}{3}
& 1) \qquad & t_a & = \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} & \hspace{4em} h_a & = \frac{1}{2} × \SI{6}{\metre\per\second\squared} × {\SI{10}{s}}² \\
& & & = \SI{10}{s} & & = \SI{30}{m} \\[1ex]
& 2) & t_v & = \frac{\SI{240}{m}}{\SI{6}{\metre\per\second}} & h_v & = \SI{300}{m} - \SI{30}{m} - \SI{30}{m} \\
& & & = \SI{40}{s} & & = \SI{240}{m} \\[1ex]
& 3) & t_t & = 2 × (\SI{10}{s} + \SI{40}{s} + \SI{8}{s} + \SI{120}{s}) \\
& & & = \SI{356}{s}
\end{alignat*}

\end{document}

• Thank you for sharing! Is there a way to number the equations like 1) 2) 3)? – Redfox87678 Jul 23 '17 at 19:56
• @Redfox87678 I can understand using double column for saving space, but numbering the equation would be confusing for the reader. – egreg Jul 23 '17 at 20:27
• Do you mean numbering the rows like an enumerated list, at the left margin? – Bernard Jul 23 '17 at 20:34
• Yes, I meant as a list. – Redfox87678 Jul 23 '17 at 20:42

Two aligned side-by-side can achieve the output you want.

\documentclass[a4paper]{article}
\usepackage{amsmath,siunitx}
\usepackage{mathtools}

\begin{document}

\begin{equation*}
\begin{aligned}[t]
t_a &= \frac{\SI{6}{\metre\per\second}}{\SI{0,6}{\metre\per\second\squared}} \\
&= \SI{10}{\second}    \\
h_a &= \frac{1}{2} \times \SI{6}{\metre\per\second\squared} \times {\SI{10}{\second}}^2 \\
&= \SI{30}{\metre}    \\
h_v &= \SI{300}{\metre} - \SI{30}{\metre} - \SI{30}{\metre} \\
&= \SI{240}{\metre}