English use of plurals with numeric (decimal) fractions is peculiar, particularly in the spoken form.
There’s no problem with plurals in general, is there? More than one, even a tiny bit more, is the plural. One and a half hours. But less than one has got to be the singular, hasn’t it?
- yes: as a vulgar fraction, it’s always a singular. No problem there: quarter of an hour, half a biscuit, a can is a third of a litre, 5/8 mile, the tolerance is 3/1000 inch
- in notations with unit symbols, those are never made plural: 0.3kg, 0.80m, 0.02s
- but here’s the wacky one: in a running text, decimal fractions suddenly turn plural. Particularly when spoken. Yup: the builders delivered 0.75 tons of gravel yesterday. Bolt broke the world record by 0.13 seconds.
- Spoken forms, for example: nought point seven five tons, point one three seconds.
- Although “point one three of a second” is also fine…
In fact, it’s so illogical that native speakers will deny it (particulary for the written form, when they’ve got time to think). And then go on to use it exactly that way in the next sentence…
Prevalence: low. But can turn up in almost any kind of text.
Frequency: high. Not that it’s a common problem, but the non-native will very often get it wrong.
Native: sometimes. Particularly when over-thinking the issue. And there’s some variation, particularly UK-US.