"a" hundred?

[tshirtsuntan]

Have heard this several times recently, as in "I would do it again a hundred per cent" surely it's "one hundred per cent"? Have possibly over thought it but it's beginning to get my goat.

I think "a hundred" is fine, in the same was as 'a dozen', 'a gross' or 'a score'.

It's fine.

Unlike 'hence why' which is my current bugbear.

When you count you say 'ninety nine, a hundred' don't you? Or there were a hundred people in the room. Or a hundred and twenty.

In fact do we ever say 'one hundred'?

"... to be the man who walked one thousand miles..."

One hundred is Scottish

Similarly, "a hundredth" is also fine, and so is "two hundredths", "three hundredths", etc.

I wish someone would explain that to athletics and swimming commentators, who insist on saying things like "three one hundredths of a second".

... but in darts it's definitely "One hundred and eighty!"

"Hundred" is a noun like any other and can be marked in the same ways. The only point to note is that most partitives require 'of', whereas these number words often quantify a noun without needing 'of' (cf. many inflected languages such as Russian, where such a usage requires the genitive case). "A hundred" (indefinite article); "the hundred or so men" (definite article); "the last hundred years" (adjective).

For some reason the plural does require 'of'. "Hundreds of thousands"; "some hundreds of pounds"; "many hundreds of people".

Thousand, million, etc. the same.