La revista vendió novecientos ejemplares en dos días.

Because la revista is the thing doing the selling in the sentence, and it is treated as a single entity: the magazine.

So the structure is:

• La revista = the magazine
• vendió = sold
• novecientos ejemplares = 900 copies
• en dos días = in two days / over two days

Even though many copies were sold, the subject is still one magazine title or publication, so revista stays singular.

Vendió is the preterite form of the verb vender (to sell), specifically:

• vender = infinitive
• vendió = he/she/it sold or you (formal) sold

In this sentence, it means it sold, referring to la revista.

So:

• La revista vendió... = The magazine sold...

The preterite is used because the sentence describes a completed event: the magazine sold 900 copies, and this happened within a finished time period, en dos días.

• vendió = sold, as a completed fact
• vendía = was selling / used to sell / sold habitually

So:

• La revista vendió novecientos ejemplares en dos días = a completed result
• La revista vendía muchos ejemplares = the magazine used to sell many copies / was selling many copies

The preterite fits better here because the sentence is about a specific outcome.

The accent mark shows where the stress goes and also helps distinguish the correct verb form in writing.

• vendio would be incorrect
• vendió is the correct spelling

The stress falls on the last syllable: ven-di-Ó

This is the standard written form of the third person singular preterite for many -er and -ir verbs:

• comió
• vivió
• vendió

Here, ejemplares means copies.

For magazines, newspapers, books, etc., ejemplar often means a physical copy of that publication.

So:

• novecientos ejemplares = nine hundred copies

It is a very natural word in publishing and sales contexts.

You could sometimes hear copias, but ejemplares is more idiomatic here for magazines, books, and printed publications.

Because novecientos means nine hundred, and it agrees in gender with the noun it modifies.

Since ejemplares is a masculine plural noun, the number is:

• novecientos ejemplares

If the noun were feminine, it would change to:

• novecientas páginas = nine hundred pages

This is something English speakers often notice because English numbers do not change for gender, but in Spanish the hundreds from doscientos to novecientos do.

Because in Spanish, exact hundreds are normally said without y before the noun.

• novecientos ejemplares = 900 copies

You use y only between the tens and units part of a number:

• novecientos uno = 901
• novecientos veintidós = 922
• novecientos treinta y cinco = 935

So 900 is simply novecientos, with no y.

Because in Spanish, a number usually goes directly before the noun:

• novecientos ejemplares
• tres libros
• veinte revistas

Using de here would be incorrect.

English speakers sometimes want to insert of, but Spanish does not do that in normal number + noun combinations.

En dos días here means in two days or over the course of two days.

It tells you the result happened within that time span.

In this sentence:

• La revista vendió novecientos ejemplares en dos días
  = The magazine sold 900 copies in two days.

This often suggests the total was reached after two days or during that two-day period.

It is different from some other time expressions:

• durante dos días = for two days / during two days
• en dos días = in two days / within two days / over two days

In many contexts, en dos días sounds more result-focused.

Sometimes, yes, but the meaning shifts a bit.

• en dos días focuses on the result being achieved within that period
• durante dos días focuses more on the duration itself

So:

• Vendió novecientos ejemplares en dos días
  = It sold 900 copies in two days.

• Vendió novecientos ejemplares durante dos días
  sounds less natural in this exact sentence, because it can suggest the selling activity lasted for two days rather than emphasizing the achievement of that total.

For this sentence, en dos días is the more natural choice.

Yes, it is perfectly natural.

Spanish, like English, often uses this kind of shorthand or metonymy, where the publication stands for the magazine as a product or brand.

So la revista vendió novecientos ejemplares means the magazine sold 900 copies, not that the paper object itself actively sold them.

English does this too:

• The book sold well
• The newspaper sold 50,000 copies
• The album sold a million copies

So the Spanish sentence is very normal.

Yes, Spanish word order is more flexible than English, but the original order is the most neutral and natural:

• La revista vendió novecientos ejemplares en dos días.

Other orders are possible for emphasis, for example:

• En dos días, la revista vendió novecientos ejemplares.
• Novecientos ejemplares vendió la revista en dos días.

But those are more marked. For a learner, the original version is the best standard pattern to use.

Yes, in this sentence la is needed because you are referring to the magazine, a specific magazine.

• La revista vendió... = The magazine sold...

Without the article:

• Revista vendió...

would not sound right in normal Spanish.

Spanish uses definite articles more often than English, and with a singular count noun like this, la is the normal choice.

The important change would be in the hundreds word.

For example:

• novecientos ejemplares = 900 copies
• novecientas revistas = 900 magazines

So the pattern is:

• masculine noun -> novecientos
• feminine noun -> novecientas

This agreement only affects the hundreds word, not the tens or units in the same way.

Very often in publishing contexts, yes.

Examples:

• un ejemplar del libro = a copy of the book
• cinco ejemplares de la revista = five copies of the magazine

But ejemplar can have other uses too, depending on context. For a learner, the safest meaning here is definitely copy.

So in this sentence, ejemplares is best understood as copies, not as something more abstract.