The difficulty of a problem was defined in terms of how long it took to complete.

问题的难易度是以解决这个问题所花时间的长短而定的。

《牛津词典》

Wait 30 to 60 minutes or however long it takes.

等30到60分钟，或需要的不管多长的时间。

《柯林斯英汉双解大词典》

Time how long it takes you to answer the questions.

记一下自己回答这些问题所需的时间。

《牛津词典》

"One of the things the World Bank measured was how long it takes to start a business.

VOA: special.2010.05.10

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

But I don't really know about how long it would take people to hack, like, the general firewall

但我不知道人们具体要用多长时间才能穿过防火墙，

理想是当密码专家 - SpeakingMax英语口语达人

At 5.5km long it is easily seen on foot, with a tree-lined walkway along the water.

BBC: Exploring Bangkok��s canals

He asked Ms Wilson how long it would take her to write an action plan.

BBC: OFMDFM Committee

So successful was the firm with this method that before long it became standard industry practice.

ECONOMIST: Idea