"干"&"做" have also usage of v..They mean doing sth.. But "干" also has the meaning of fuck(...) as the slang which is alway used by the Northeast Chinese.&execpt the usage of v. for "干" ,it also has the usage of a.&ad..Just like dry ,for instance "干毛巾dry towel" ;like waterless ,干洗剂dry cleaner;like empty,外强中干 outwardly strong but inwardly weak;like futilely ,我干等了他半天 i wasted a lot of time for him.and so on .All come from Google powerword. I suggest u to use the sofeware of Google powerword &hope u lean Chinese with cheerful mind.

this is a commen question for foreingers learning Chinese. there are some difference and similarity for "干"&;"做"as verb. when you say"do one's homework" you can only say:做作业，never say"干作业"，and the same as"做试验"“做饭”“做衣服”“做朋友（make friends with sb）”.... when you say "干"，you do some work harder,or even fight/strugle, like“干得好(well done)”"干活"“来了就干（do a job as soon as I come）”here "干" can be replaced by "做"，and no different meaning. there is only few words can't be replaced by "做"，like"大干300天（work energetically for 300 days）" in your 2 sentences, there is no difference,你在干什么？ 你在做什么？ 你现在在做什么呢？你现在干什么呢？ they make the same sense.

actually there's no big difference. but "你在干什么呢？ "seems more casual and if you use a strong tone, it can express a mood of unsatisfaction. eg: you find sb. use your things without your permission, you can say "你在干什么呢！”（obviously you know what he or she is doing)

the same about them! oniy a little difference

Hi Juan, 做always add more specific things like 做饭 cooking 做作业doing homework but 干can not add such specific things it always connect with some general things like 干活 doing something .Give you an example : 你在干什么？ ——做家具 What are you doing? Making furniture These are just the basic differece I hope you can understand it:)