I want to specify a room in a building. I come up with three optimum sentences -
1-) In room_number at building_name
2-) In room_number in building_name
3-) At room_number in building_name
Though, I prefer to use the third one. But still, I want to know the best sentence in this case.
Though this is the only full phrase I wanna use, you can consider the full sentence as - "The meeting will be held in room_number in building_name."
I think the best sentence is the second one.
In fact, choosing location prepositions is sometimes a problem.
But I would recommend you the following rule:
The choice of the preposition depends on the kind of place.
If it is some volume, we use IN.
If it is some surface, we use ON.
AT is used when the former ones aren't appropriate (for example, at work, at the hotel, at the station, at the bus stop, etc.).
Sometimes the choice depends on what the speaker means.
For example, it's possible to say both 'in the office' or 'at the office'.
Here the choice depends on your view of this office.
If it's just a 'room for business', use IN .
If you mean 'at work' (not exactly in this room), use AT.
