很难估计这次旅行要花多长时间。
It's difficult to judge how long the journey will take.
你原打算待多长时间？
How long a stay did you have in mind?
你干现在这工作多长时间了？
How long have you been in your present job?
我正要出去，用不了多长时间。
I'm just going out ─ I won't be too long.
你做家庭作业用了多长时间？
How long did you spend on your homework?
扬帆飘舟
