用2,0,4,6,9着5个数字可以组成数字不重复的五位偶数共有多少个?

狒狒给的答案是78,可我觉得应该是72,麻烦各位帮忙解答一下哦!

if the unit digit is 2 or 4 or 6 -- C3,1 cases

the highest digit has C3,1 cases

the rest 3 digits have P3,3 cases

if the unit digit is 0 -- 1 case

the highest digit has C4,1 cases

the rest 3 digits have P3,3 cases

total = C3,1 * C3,1 * P3,3 + 1 * C4,1 * P3,3 = 78

I think 78 is right.

P(4,4)*C(4,1)-P(3,3)*C(3,1)=78