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2) A car with four wheels is a four-wheel car.

3) An animal with four legs is a four-legged animal.

4) A building with five stories is a five-story building.
How do we know when to use noun plus pp and when to use noun plus ed?
Why can't we say "five-storied(which has five stories) and four-wheeled"?
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JigneshbharatiHow do we know when to use noun plus pp and when to use noun plus ed?

As far as I know, all of those kinds of compounds consist of a number and a past participle. The only exception is with parts of the body (one-armed man, five-eyed monster).

JigneshbharatiWhy can't we say "five-storied(which has five stories) and four-wheeled"?

An alternate spelling of "story" is "storey" when it refers to levels of a building, especially in British English.

You will occasionally see all of the following:

four-wheel, four-wheeled, five-story, five-storey, five-storied, five-storeyed

But the ones given as examples in your post are the more common ones.

CJ

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Jigneshbharati2) A car with four wheels is a four-wheel car.

We only use this modifier with a car when it has an unusual number of wheels. e.g. A three-wheeled truck.

A fourwheeler is a dirt bike.