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So, the mass. Is the volume of this sphere.
此處的質量是球體的體積
So, that's a meter cubed you throw in there.
因此可以把米的立方代進去
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,
那么就變成了，能量等于米^5/秒^2能據此計算出原子彈的威力
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.
計算出俄羅斯和美國的原子彈的威力比從而解密了當時世界的頂級機密
That's a hard problem.
這個是很難的問題
Figuring out what Facebook's retention rate is not a hard problem.
計算出Facebook的用戶留存并不困難
How many people are there on the internet?
全世界有多少網民？
Give or take someone throw something out.
說個大體數
2.4 billion, 2.3 billion. Something like that right?
有人說24億，有人說23億，差不多就是這么個數
Okay, Facebook's banned in China. So. What now?
Facebook在中國是被禁的，那么還有多少網民?
About a billion. About 2 billion? 2 billion. So 2 billion people on the internet.
約10億約20億？好的 20億網民
Facebook in their last earnings call said something around 1.3 billion in terms of the number of active users.
Facebook在上次收益報告中稱約有13億活躍用戶
You can divide those numbers by each other.
可以把兩個數相除
And yeah, that won't give you the right answer.
結果是不準確的
Course it's not gonna give you the right answer.
當然結果不準確
But it's gonna give you close enough to a ballpark figure.
但是可以讓你大體了解
Of what the retention rate looks like for Facebook.
Facebook的用戶留存率
If we signed everyone on the internet up, and then you will know it is higher than that.
如果把全世界網民都算上的話得出的結果要比剛才的數大一些
Similarly if you look at Whats App, they've announced six hundred million active users.
同理，如果看Whats App的話他們公司宣稱有6億活躍用戶
How many people have smart phones? You can figure out that number.
有多少人有智能手機呢？你可以估算出來
That number is out knocking around.
這個數據比較好找
It can give an idea of how many users there are.
從而可以大體知道有多少用戶
Amazon has had a pop at signing up almost everyone in the United States.
Amazon很火幾乎所有美國人都注冊了
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.
你可以知道在美國有多少網民從他們公布的數據可以推出亞馬遜有多少用戶存留
Different verticals need different terminal retention rates for them to have successful businesses.
公司類型不同用于判斷公司是否成功的留存率標準也不同
