排列组合:
P(6,5)=6*5*4*3*2=720 (错误)
更正:之前的确实考虑不周全,谢谢kittie_gong同学的提示.下面的算式,我先解析下:
5本书给5个人,那么有书的每人一本,即1.1.1.1.1,最后=P(6,5);
5本书给4个人,其中一人得2本,即:2.1.1.1 ,C(5,2)*P(6,4);
5本书给3个人,有两种分法,2.2.1或者3.1.1,C(5,2)*C(3,2)*P(6,3)+C(5,3)*P(6,3);
5本书给2个人,3.2,C(5,2)*P(6,2);
5本书给1个人,C(6,1),
最后结果:
P(6,5)+C(5,2)*P(6,4)+C(5,2)*C(3,2)*P(6,3)+C(5,3)*P(6,3)+C(5,2)*P(6,2)+C(6,1)
猜你喜欢
- 1now ,having __ ___ ________ _______a foreign language is more important than ever before
- 2Students should be encouraged to use ___Internet as ___resource.
- 3It is getting and ---(warm) in spring
- 4810除以18简便计算怎么算谢谢了,
- 5哪个成语的意思是:应该有的全有了,表示一切齐备
- 6粗食盐中常含CaCl2、MgCl2、Na2SO4杂质,需按一定顺序加入(初三化学)
- 7甲、乙两列火车分别从A、B两地同时出发,相向而行,经过1.5小时在离中点18千米处相遇.已知甲车速度是乙车的1.2倍,相遇时,两车各行了多少千米?
- 8甲乙两人在400米环形跑道上练习跑步,甲每秒5.5米,乙每秒4.5米.
- 9已知关于x的方程x2-2(k-1)x+k2=0有两个实数根x1,x2. (1)求k的取值范围; (2)若|x1+x2|=x1x2-1,求k的值.
- 10he likes science best because it's interesting 对 it's interesting 提问