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So, the mass. Is the volume of this sphere.
此处的质量是球体的体积
So, that's a meter cubed you throw in there.
因此可以把米的立方代进去
So you've got meters the 5 over seconds the minus 2, and he was able to use that to just figure out what the power of this atomic bomb was,
那么就变成了，能量等于米^5/秒^2能据此计算出原子弹的威力
what the ratios of the power between the Russian and US atomic bomb, and essentially reveal one of the top secrets that existed in the world at that time.
计算出俄罗斯和美国的原子弹的威力比从而解密了当时世界的顶级机密
That's a hard problem.
这个是很难的问题
Figuring out what Facebook's retention rate is not a hard problem.
计算出Facebook的用户留存并不困难
How many people are there on the internet?
全世界有多少网民？
Give or take someone throw something out.
说个大体数
2.4 billion, 2.3 billion. Something like that right?
有人说24亿，有人说23亿，差不多就是这么个数
Okay, Facebook's banned in China. So. What now?
Facebook在中国是被禁的，那么还有多少网民?
About a billion. About 2 billion? 2 billion. So 2 billion people on the internet.
约10亿约20亿？好的 20亿网民
Facebook in their last earnings call said something around 1.3 billion in terms of the number of active users.
Facebook在上次收益报告中称约有13亿活跃用户
You can divide those numbers by each other.
可以把两个数相除
And yeah, that won't give you the right answer.
结果是不准确的
Course it's not gonna give you the right answer.
当然结果不准确
But it's gonna give you close enough to a ballpark figure.
但是可以让你大体了解
Of what the retention rate looks like for Facebook.
Facebook的用户留存率
If we signed everyone on the internet up, and then you will know it is higher than that.
如果把全世界网民都算上的话得出的结果要比刚才的数大一些
Similarly if you look at Whats App, they've announced six hundred million active users.
同理，如果看Whats App的话他们公司宣称有6亿活跃用户
How many people have smart phones? You can figure out that number.
有多少人有智能手机呢？你可以估算出来
That number is out knocking around.
这个数据比较好找
It can give an idea of how many users there are.
从而可以大体知道有多少用户
Amazon has had a pop at signing up almost everyone in the United States.
Amazon很火几乎所有美国人都注册了
You know how many people are online in the US, and you've got a good idea of how many customers Amazon are from the numbers they throw out.
你可以知道在美国有多少网民从他们公布的数据可以推出亚马逊有多少用户存留
Different verticals need different terminal retention rates for them to have successful businesses.
公司类型不同用于判断公司是否成功的留存率标准也不同
