plural nouns after numbers

[Vladv1]

Dear native speakers, I know that in patterns like "a three-day party", "a five-minute song" we use nouns in singular? (NOT a five-minuteS song). But I remember somebody saying there was an exception where the noun after the number in the pattern similar to the examples I gave was PLURAL. I don't remember the noun itself. Could you please be so kind as to help me out.

 

[SoothingDave]

I can't think of any exception.

You can have twenty 2-meter cables.

 

[jutfrank]

I don't think there are any exceptions.

 

[Vladv1]

I can't think of any exception.

You can have twenty 2-meter cables.

Is " we have five five-year plans" correct

 

[jutfrank]

Yes.

 

[emsr2d2]

Is "We have five five-year plans" correct?

It is but it doesn't fit the pattern you're asking about. You're suggesting that there's a noun where "year" comes in that sentence that could be a plural.

 

[Annabel Lee]

Dear native speakers, I know that in patterns like "a three-day party", "a five-minute song" we use nouns in singular? (NOT a five-minuteS song).

If I heard "a five-minutes song" or "a three-days party," I would not find the phrases ungrammatical but would, rather, assume that the speaker had chosen to use a slightly archaic, plural possessive construction:

a five minutes' song
a three days' party

 

[PeterCW]

The only example that I can think of is the "Hundred Years' War" being written without the possessive. It is a common mistake and I found two examples on the first page of a Google search.