workers是複數，用an是否不對？

We are employing an extra 500 workers. ~ correct

In this kind of construction, we are thinking of "a single group of people” (a quantity). That's why we say 'an extra 500 workers” rather than '500 extra workers'. It seems that the emphasis is on the word “extra”. We use “an” in front of words that begin with vowel sounds.

Additional examples:
Recently he's been working an extra two hours a day.
– from Cambridge English Dictionary.

The federal government will lay off an extra 2000 civil servants
– from a local newspaper

An additional 347 people died each year from drowning in boating-related incidents.
– from U.S. Centers for Disease Control and Prevention



2012-07-17 10:03:19 補充：
“Some speakers do not pronounce the ‘h’ at the beginning of hotel and use ‘an’ instead of ‘a’ before it. This now sounds old-fashioned.”
- quoted from Oxford Advanced Learner’s Dictionary:

a hotel, a historical book ~ both in writing and speaking

回應答案002:


That's why we say 'an extra 500 workers” rather than '500 extra workers'

應改成 That's why we say 'an extra 500 workers” rather than 'extra 500 workers'

We are still short of funds.
We need another 100,000 dollars.

Another and dollars go together.

We are employing extra workers.
We are employing 500 extra workers.
We are employing an extra number of workers.
We are employing an extra 500 workers.

The words a (an),and the are generally called "articles" a (an) is the Indefinite Article.
the the Definite article.
An is used sometimes even before a normally aspirated (h) when the stress does not fall on the first syllable of the word, eg:-an hotel,an historical book.
When followed by a vowel sound,extra,it becomes "an extra...."
Hence "an extra 500 workers" is a phrase,acting as an object.
Hence,We are employing an extra 500 workers.