Translation:Hi, can you tell me where the opera house is?
True, but why not "can you say where the opera house is?" - I think this is probably a better translation. As the original commenter said, there's no indication in the Finnish who this information is being given to. The "correct" translation sort-of suggests "yes I can tell you, specifically, where it is, but I might not tell him or her, for example"
You assume wrongly. The 'me' should not be omitted from the English translation or it sounds stilted.
"Can you tell ... ?" usually is employed where you are really meaning "Can you guess ...?" An artist on kids' TV used to have a catch-phrase "Can you tell what it is, yet?" as he was daubing paint (seemingly randomly) on a huge piece of paper.
I'm not a linguist, so can't begin to fathom / explain why inclusion of 'me' is necessary for the correct translation, here ... it just is.
If the Finnish sentence is using the verb "osata" which means "to know how", I really don't see the reason to only allow the translation of the meaning "will you please tell me" when it literally has the combination of "osata sanoa" (can tell/know how to tell) suggesting it might actually be quizzing someone. I'm just a student so might be wrong but it kind of makes sense.
Could we not use kertoa here (to tell) osattko kertoa .. (can you tell)
You can. Osaatko sanoa sounds a bit more natural. With kertoa it sounds more formal.
Yes, you wouldn't say "do you know how to say" in English. :-) The Finnish question isn't actually about the ability to express a particular set of words, but a request for information... so in English you'd say "do you know", "could you tell me", "can you tell me", or something like that.
The satirical would give the answer to "do you know...?" as "yes, thanks." In other words, in english that formulation does not actually ask the recipient to deliver possibly available information.
Wheras ' Can (or politely the conditional form, 'could") you tell me' actually requires an answer.
Hope that is clear. It is quite subtle in english.