The older kind of submarine used in World War Two could stay under water for only about forty-eight hours.

VOA: special.2010.06.11

And if you are prepared to stand up for about two and a half to three hours to watch a play,

而且你要准备好了站上大约两个半小时到三个小时，去看一场戏剧，

莎士比亚环球剧院 - SpeakingMax英语口语达人

That is because out of three days and two nights, the families will only see each other for a total of about 11 hours.

VOA: standard.2009.09.26