It will certainly work as a possible transaltion, but the emphasis would shift: "зачем"="for what purpose" while "почему=why". I.e. "Почему вы спрашиваете?" will allow the answer "because I didn't know that" or "because I've forgotten that" while "Зачем вы спрашиваете?" would not.
Почему ты спрашиваешь?
Conjugation classes in Russian behave in a very predictable manner, unless you have a really irregular verb like есть (ешь / едите), хотеть (хочешь / хотите) or дать (дашь / дадите ; создать works similarly).
Is there a reason why вы is used mostly in this course? Is that the same in 'real life'?
Actually, This course has about 200 sentences with вы and about 360 with ты. I did not count the oblique forms, though.
Then it's just my imagination xD. I really felt that вы was used way more frequently than ты.
Thanks for replying
Regarding on your progresses, you may have randomly more phrases with вы than ты, independently of the course -if I get right how duolingo works :)
Спрашивать/спросить is asking a question, просить/попросить is asking a favour.
Is спрашивать perfective and then спросить imperfective? Or is it the other way around?
In my opinion, "Why do you ask?" would be more natural in English. Can this sentence be translated that way?
Просить is the verbs that means asking for a favour or an object. Asking a question is спрашивать (also used for asking someone to call a person you came for or wish to speak with)
When is it okay to omit personal pronouns? E.g., does Почему спрашиваете sound fine?