How long is the course?

这门课程开多久？

《牛津词典》

How long is the tunnel?

这隧道有多长？

《柯林斯英汉双解大词典》

How long is the River Nile?

尼罗河有多长？

《牛津词典》

They say it will help scientists better understand how to protect long-beaked echidnas and the areas where they live.

VOA: special.2009.07.07

You told me that you've written plays by yourself. How long did it take you to finish them?

你告诉我你自己写剧本。写完一个剧本要多久呢？

灵感从何处来 - SpeakingMax英语口语达人

One of the things you could imagine is just try it on and input, see how long it takes.

你们想出来的方法只是可能就是通过,输入来试试，看运行时间会有多长。

麻省理工公开课 - 计算机科学及编程导论课程节选

At dinner with a group of journalists, U.S. Treasury Secretary Lawrence Summers was similarly unhelpful about how long the U.S. boom could last.

CNN: ASIANOW - TIME Asia | Davos 2000: Time Out

The bank CEO declined to give a timeline but said it "depends how long the Germans hold out... how long the German population is willing to buy into supporting" fiscal union.

CNN: Should the euro never have existed?

Mr. THOMPSON: I don't know how long Mr. Rumsfeld intends to stay but I do know this - he's not going to leave under fire.

NPR: Donald Rumsfeld, Secretary of Self-Defense