組合問題(5 boys and 1 girl 排成一行..if girl 唔可以排頭and 尾...有多少排法...?)

5 boys and 1 girl 排成一行..if girl 唔可以排頭and 尾...有多少排法...??
ans .and solution..
5個男孩的排法有
5! = 120種
而女孩子可以排在2，3，4，5四個位置所以排列法共有
120 x 4
= 480

e道得YS啱

120 x 4

= 480

5 boys and 1 girl 排成一行..if girl 唔可以排頭and 尾...
=...b y b b b b
=...b b y b b b
=...b b b y b b
=...b b b b y b

共有 4 種排法.....

如計埋排頭and 尾就有 6 種排法

Assume b=boy, g=girl
possible position of g =3
That is
bgbbb, bbgbb and bbbgb

For each case, the problem is only about
the rest 4 boy is arranged
there are 4!=4X3X2X1=24 chance
So, total 3X24=72 chance

2007-06-06 23:07:36 補充：
sorry, 看錯題Assume b=boy, g=girlpossible position of g =4That is bgbbbb, bbgbbb and bbbgbb, bbbbgbthe rest 5 boy is arrangedthere are 5!=5X4X3X2X1=120 chanceSo, total 4X120=480 chance