Struggling with this one, I didn't know תודה רבה was informal, I always though it can be used to say "thank you".
It's not informal, it is used more as "thank you" or "thank you very much", but in Hebrew we don't really have this distinction between formal and non-formal so I guess it can be used casually as well.
Thank you or I should say תודה רבה. It gave me "wrong answer" for translating as "Thank you" so maybe it needs to be changed?
Aha! I understand, thank you.
I'm don't really agree. While your translation is correct from a literal standpoint, the phrase תודה רבה is basically slang for "thank you" or "thanks". The distinction between that and "thanks a lot" is insignificant.
Well, technically there a distinction, and I think it's important for those studying Hebrew to be aware of that. But you're right, we use them interchangably. Duolingo now accepts "thank you" as a correct answer.
Does anyone have an idea when to use ת and when to ט when writing Hebrew words that has "T" sound?
There is no rule, you just have to memorize the spellings, just like with English words that have the same sound but different spellings: write/right, red/read, no/know; ceiling, cite, cemetery, with a "c" rather than an "s" though both letters make the "s" sound, knee not nee, phone not fone, etc. At one time, the two letters were pronounced differently. This distinction is not observed by most people anymore. ט was/is pronounced in the throat. ת even had/has more than one pronunciation depending on its position in a word and the historical time and location of the Hebrew speakers. It is interesting linguistic history but we don't have to know it, or learn it, to study standard Modern Hebrew.
The word תודה is "thank you" - תודה רבה is "thank you very much" or "thanks a lot"
"Thank you" is still rejected! The Duolingo team is very slow in correcting mistakes.