"You can get there in thirty minutes."
Translation:Ci puoi arrivare in trenta minuti.
"Tra" has a meaning of arriving "within" the period of time stated. When I am in Italy and someone asks me when I will be arriving, I nearly always says "tra trenta minuti" (or whatever maximum period of time left until I arrive). I'm not a native speaker, but I would use "in" if I were being more precise, i.e. I would say "in trenta minuti" to mean I would arrive in 30 minutes (not before, like if I on a train and I know the time it will be arriving) and "tra trenta minuti" to mean I would be there sometime within the next half hour, perhaps earlier. Again I am not a native speaker, so I welcome corrections.
Andreas: Both Ci puoi arrivare... and Puoi arrivarci...are equally correct. Your last translation: "You can get us in 30 minutes" is incorrect for the Italian. Ci does not mean 'us' in that sentence and 'arrivare' doesn't mean to 'get' someone or something. Arrivare is NOT a transitive verb.
Thanks to everyone for the good comments - especially Mr. Marninger and LynnSearn. Thanks to your help, I realized that "ci" is part of the transitive verb "arrivarci". Before that I tried to guess what the "ci" should be at the beginning of the sentence and thought it was "we" Only after your help did I understand that "Ci puoi arrivare in trenta minuti." or "Puoi arrivarci in trenta minuti." really means "You can get there in thirty minutes". :-))