Learn Finnish: Johtajat ovat varanneet neuvotteluhuoneen. - The managers have booked the conference room.

No, this sentence is actually in the active voice! It specifies exactly who did the booking: johtajat (the managers). In the active perfect plural, you use ovat plus the plural active participle varanneet. Language lessons often include active sentences like this to help you contrast them with the new passive structure. To make it passive (The room has been booked), you would use the passive perfect: Neuvotteluhuone on varattu.

Why does varata become varanneet here?

Varata (to book) is a verb type 4. Because the managers are actively doing the booking, we need the active past participle plural. You take the infinitive stem varan- and add the plural ending -neet. If this were a passive sentence, we would use the passive participle instead (varattu).

Why does the object neuvotteluhuoneen end in -n?

In Finnish, when an action is fully completed (the booking is successfully done) and there is a specific subject doing the action (johtajat), a singular object takes the -n ending. This is the accusative case that looks just like the genitive, and it signals a total, finished action.

How would the object change if we used the passive perfect taught in this lesson?