# How to punctuate math fractions?

I was doing the Writing and interpreting decimals exercise on Khan Academy and was asked the following question:

What is nine and three hundred two thousandths in numerical form?

I read it as "What is nine and three hundred... two thousandths", i.e. 9 and 300/2000 instead of "What is nine and three hundred two... thousandths", i.e. 9 and 302/1000.

Should there be a punctuation difference between the two?

• If I'm not mistaken (though it's possible I am), it should be three-hundred-two thousandths for 302/1000 and three-hundred two thousandths (two-thousandths?) for 300/2000. On the other hand, – Kevin Oct 20 '13 at 1:36
• Three hundred two thousandths is ambiguous, as you note. I'd use three hundred over two thousand and either three hundred two one thousandths or three hundred two over a (or: one) thousand. Or I'd reduce it to lowest terms by dividing out common factors. `:-)` – msh210 Oct 20 '13 at 2:03
• In BrE, it becomes clearer: 'nine and three hundred and two thousandths' (=9.302). But 'three hundred and two and three hundred and two thousandths' is getting a little more opaque. – Edwin Ashworth Oct 20 '13 at 13:18

## 1 Answer

Math has its own idioms that are a subset of "normal" English. I can see where there might be some confusion to someone unfamiliar with those idioms, but one would never read or write "300/2000" as "three hundred ... two thousandths". It would be "300 over 2000" or "300 out of 2000" or possibly reduced to "3 out of 20".

So I would argue it is mathematically unambiguous as written and additional punctuation is unwarranted.

Adding hyphens between the words as Kevin suggested in the comment ("three-hundred-two thousandths) might avoid some confusion, but is inconsistent with the typical grammar rules of hyphenating numbers.

• "one would never read or write '300/2000' as 'three hundred ... two thousandths'". Do you have a source for this assertion? – Ben Lee Nov 5 '13 at 16:48