數學一問（要有資料來源）

圖片參考：http://upload.wikimedia.org/math/d/c/9/dc9ebca2704bffee110d8260ed7d1666.png

where:


r is the size of each permutation,
n is the size of the sequence from which elements are permuted, and
! is the factorial operator.

這是permutation, 現在 n 和 r 都係 10:
= 10! / (10 - 10)!
= 10! / 0!
= 3,628,800 / 1
=3,628,800


Remarks:
n!=n(n-1)(n-2)...(n-n+1)
10!=10 x 9 x 8.......x 2 x 1
0! = 1

2007-04-10 14:15:27 補充：
資料來源http://en.wikipedia.org/wiki/Permutation

10x9x8x7x6x5x4x3x2x1 = 3628800