从1,3,5,7,9任取2个数字,从0,2,4,6,8中任取2个数字?

2024-12-15 14:34:18
推荐回答(1个)
回答1:

分类:
1)偶数取到0,再取另一个C(4,1),奇数取法C(5,2),再分类:0在个位时A(3,3) ,
0不在个位时,只能另一偶数在个位,C(2,1)A(2,2)
2)偶数不取0 则C(4.2)C(5,2)C(2,1)A(3,3)
共有:C(4,1)C(5,2)*【A(3,3)+C(2,1)A(2,2)】+C(4.2)C(5,2)C(2,1)A(3,3)=1120