# Compound fractions (i.e., “mixed numbers”) look bad in displaystyle

I find that in display mode, fractions that represent simple rational numbers look way too big. For instance, consider this case:

$$a = \frac12(b+c)$$


The fraction gets inordinately large compared to everything else in the line.

I understand that it's display mode, and that's supposed to happen, but the value of it is for fractions with complex contents, giving them space to spread out and not be squished. For a simple rational number, it seems like it's far too large.

This problem is worsened in the case of (what US elementary schools call) compound fractions, or mixed numbers. Consider this:

$$\vec v = \left\langle 3\frac12,-6,0 \right\rangle$$


This comes out with one enormous fraction larger than everything else dominating the scene, enlarging the angle brackets, and not looking at all like it is part of a single numerical value with the preceding 3.

My solution in such situations has been to put \textstyle at the front of the display math, but that has two disadvantages. First, it seems stupid to say, "display--no wait, not display!" Second, it makes everything in the whole section textstyle, not just the fractions.

The way I'm currently handling this is as follows, where mn stands for "mixed number."

\def\mn#1#2#3{#1{\textstyle\frac{#2}{#3}}}
...
$$\vec v = \left\langle \mn312,-6,0 \right\rangle$$
$$a = \mn{}12(b+c)$$


Is there a common way to handle this I don't know about? Does it not look ugly to anyone else? Is my solution sensible?

Thoughts welcome.

• The amsmath package provides \tfrac. Don't use  with LaTeX. – egreg Jun 13 '13 at 14:34
• amsmath defines \tfrac for text style frac – David Carlisle Jun 13 '13 at 14:35
• As a general proposition, you may want to write \frac{1}{2} (or \tfrac{1}{2}, if you use the amsmath package) instead of \frac12 -- the resulting gain in readability/scannability by human eyes must surely outweigh the "cost" of typing two sets of curly braces. – Mico Jun 13 '13 at 14:48
• Compound numbers should be avoided. In most cases, nothing is gained in comparison to either simple fractions or decimal numbers. If the numbers concerned are large like 123+45/678 you gain no clue about the scale of the fraction and you gain no easy clue about divisibility. If the numbers are small like 1+2/3 one can use 5/3 just as easily. – Toscho Jun 13 '13 at 18:18

egreg gave me exactly what I needed: I was unaware of \tfrac and \dfrac in amsmath. Thank you very much!