Using 在哪儿 as a question.
How do I ask?:

Do you know where the subway is?
你知不知道地铁在哪儿？
or
你知道地铁在哪儿吗？

Or is there another way to ask this question?

Please correct my Chinese.
Thanks for your help.

Question

Using 在哪儿 as a question.
How do I ask?:

Do you know where the subway is?
你知不知道地铁在哪儿？
or
你知道地铁在哪儿吗？

Or is there another way to ask this question?

Please correct my Chinese.
Thanks for your help.

Answer

你知不知道地铁在哪儿？→I wonder whether you know where the subway is or not?
你知道地铁在哪儿吗？→Do you know where the subway is?
The 2 sentences have the same meaning as a matter of fact and 2nd one sounds more native

But if I ask someone where the subway is,I'd like to say:
请问，您知道地铁在哪吗？
Cuz you have to show your respect to the one asked in Chn

Answer

They are definitely same.
你知不知道地铁在哪儿？=你知道地铁在哪儿吗？=你知道不知道地铁在哪儿？＝地铁在哪儿？你知道吗？＝你能告诉我地铁在哪儿吗？=请问地铁在哪？
The key phrase is just ”地铁在哪？“, the rest part is changeable.

Answer

你有skype吗  我的是frank.liangyong.101   我们可以语音的 用中文   我现在在线的啊

Answer

this difference is just like "do you know where the subway is" and "do you know where the subway is or not"