# Counting Rules

nPx= n ! / ( n- X ) !

Counting Rules點計？

請用中文解釋一下...

Update:

咁我點知個Ｎ係成幾多呢﹑

咁個Ｐ又係Ｄ咩？

### 1 Answer

Rating

- Anonymous1 decade agoFavorite Answer
P 係排列意思囉

n 係 total 共幾多數咩

x 係取幾多數咩

! 係階乘

for e.g

n for 6, x for 2

it can be write down as

6P2 = 6! / ( 6 - 2 )! = 6! / 4! = 6 * 5 * 4! / 4! = 6 * 5 = 30

P.S 6! = 6 * 5 * 4 * 3 * 2 * 1

Source(s): 自己

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