来自《耶鲁大学开放课程：金融理论 第7集 第7集》

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  this is year 1, so at year 12, 24 dollars has become 48.
  这里是第一年 24年后24变成48
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  So it's a very good approximation.
  近似的结果非常好
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  And so 7 percent it's supposed to take a little over 10 years.
  在7%利率水平上需要10年多一点
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  So at 10 years you're not quite there, but 11 years you're past it.
  比10年多一点但是不到11年
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  So you can see how we're starting with 24,
  你看我们从24开始，
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  you can see how good the doubling rule is.
  翻倍法则效果非常好
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  So that's just something to keep
  继续做**翻译可能不好
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  so we can now do in class lots of concrete examples
  因此我们课上可以解很多例子
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  without having to take out our calculators and stuff
  而不用计算器
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  because we can do them in class in your head.
  因为我们课上可以心算
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  All right, so let's just do that now.
  现在我们来做一个
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  Okay, so in fact why did I pick 24 dollars?
  为什么我选24块钱做例子呢