Learn Swedish: Arkeologen hade hittat skatten innan den blev placerad på museet. - The archaeologist had found the treasure before it was placed in the museum.

This sentence uses a dynamic passive (blev + past participle). In this structure, the past participle acts like an adjective and must agree with the subject. The subject here is den (which stands for the en word skatten). Because den is an en word, the participle takes the en form placerad. If the subject were an ett word, it would be blev placerat, and if it were plural, it would be blev placerade.

Why use the past perfect hade hittat in the first half of the sentence?

The past perfect (hade + supine verb) is used to show that an action happened before another action in the past. The archaeologist found the treasure first (hade hittat), and then, later on, it was placed in the museum (blev placerad).

Wait, shouldn't "the museum" be "museumet"? Why is it museet?

The base word is ett museum. In Swedish, many ett words that end in -um (often borrowed from Latin) drop the -um before adding the definite ending -et. Because of this rule, museum becomes museet, not "museumet".

The English translation says "in the museum", so why does the Swedish sentence use instead of ?