五辆车分别展示于五个地方，其中3 辆红色，1辆黄色、1辆黑色，everyone is identical except for the color (考试中的原文亦如此)，问有多少种排列方式
解：26
与我的答案不同啊！为什么会得26？？？！作者: likerock 时间: 2003-3-29 03:55
My answer is P(2, 5) = 20.
My solution is this.
Assign number to each slot for car, say 1, 2, 3, 4, 5. Since there are three identical red cars, I don't care the permutation of them. So the question will become "To put 5 numbers in 2 different cars, what's the permutation?". Once I put the numbers on the other cars, the red cars numbers are determined. So it's P(2,5) = 20. Anything wrong here?
