一念情起九月如歌txt:Math!!!!Math~~~~~

来源：百度文库 编辑：查人人中国名人网 时间：2024/07/08 20:47:04
The average of P number is x and the average of N number is y. What is the average of all the (P+N) number?

x+y

(P*x+N*y)/(x+y)

(P+N)*xy /(Py+Nx)

(P*X+N*Y)/(P+N)
加权平均数

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