Tachtig studenten doen mee.

Because the subject is plural: tachtig studenten.

Even though tachtig is a single number word, the whole subject refers to many people, so Dutch uses the plural verb form:

• Eén student doet mee.
• Tachtig studenten doen mee.

So doen agrees with studenten.

The full verb is meedoen, but meedoen is a separable verb.

In a normal main clause, Dutch splits it:

• Tachtig studenten doen mee.

Here:

• doen = the conjugated verb
• mee = the separable prefix, placed at the end

But in other forms, it stays together:

• infinitive: meedoen
• subordinate clause: dat tachtig studenten meedoen
• with te: om mee te doen

This is a very common Dutch pattern.

Meedoen means to participate, to join in, or to take part.

It is a very common everyday verb. It often suggests active involvement in something.

For example:

• Wil je meedoen? = Do you want to join in?
• Veel studenten doen mee. = Many students are participating.

A more formal alternative is deelnemen.

Sometimes yes, but not always.

If you mention the activity, you often use meedoen aan:

• Tachtig studenten doen mee aan het onderzoek.
• Zij doet mee aan een wedstrijd.

In Tachtig studenten doen mee, the activity is simply not stated. The sentence just says that eighty students are participating.

Because tachtig studenten is an indefinite plural phrase, just like English eighty students.

Dutch does not need an article here:

• Tachtig studenten doen mee. = Eighty students are participating.

If you wanted to mean a specific group, you could say:

• De tachtig studenten doen mee. = The eighty students are participating.

So no article is normal in the original sentence.

Usually not.

In Dutch, student usually means a student in higher education: college or university.

For younger school students, Dutch more often uses:

• leerling = pupil/student
• scholier = school student

So this is a common difference from English, where student can be broader.

Tachtig is pronounced roughly like TAKH-tikh.

Important points:

• The ch is the Dutch throat sound, not the English ch in chair.
• The first syllable is stressed: TACH-
• The second syllable is weaker.

It is related to acht (eight), so tachtig is literally the Dutch word for eighty.

The sentence follows normal Dutch main-clause word order:

• Tachtig studenten = subject
• doen = finite verb
• mee = separable prefix at the end

So the pattern is:

subject + finite verb + rest + separable prefix

That is why the sentence is:

• Tachtig studenten doen mee.

and not:

• Tachtig studenten mee doen.