Should Numbers be Followed by (Numerals)?
That is, do you say you want to order five (5) of something, or just five or just 5? Depends on who you ask. Grammar Girl, of whom I am a great fan, says it is “a relic of legal writing.” FumbleFingers says, “Have people already forgotten how to write cheques?” (FumbleFingers must be British.) And others throw in examples of why it is/is not needed.
Let’s look at checks for a minute. You have to put the amount in numerals (digits) as well as words. If the two don’t match, the bank rejects it. And that’s the point. To avoid mistakes. So, it’s easy to see why it be required in almost all technical writing and a lot of grant writing. And it is used in legal documents so nobody can say the misread the number.
Let’s keep in mind, too, that originally, documents were handwritten, so mistakes would not be uncommon. Then, enter the mimeograph (remember the smell of those newly-minted sheets? Ahh!), which was not always very clear. Copies being what they are now, there is much less chance of confusion. Still, digits are not very clear in some fonts. So, here’s what I think: If it is very important that the number be communicated accurately, use both. Otherwise, do what you want to do.