[問題]GWD13-3

[blacklilu]

Each participant in a certain study was assigned a sequence of 3 different letters from the set {A, B, C, D, E, F, G, H}. If no sequence was assigned to more than one participant and if 36 of the possible sequences were not assigned, what was the number of participants in the study? (Note, for example, that the sequence A, B, C is different from the sequence C, B, A.)

A. 20
B. 92
C. 300
D. 372
E. 476

請教一下這題，提議有些搞不懂。謝謝各位大大。
Ans : C

[homaru]

C(8,3)*3!-36=336-36=300

[Annesft]

被蛋大這麼一點...任督二脈好像都通了
真是太~利~害~了

[FannyHsieh]

我不是很懂為什麼C(8,3)後還要再乘上3!......有哪位牛牛可以解釋一下嗎@_@

[charles4011]

p(8,3)=8!/5!=336(有sequence關係,所以用P) 再說no sequence was assigned to more than person and 36 of the possible sequences were not assigned~所以在336-36=300

[chris8888]

像這種類似密碼或是編號的題目最好用P(m, n) 不要用 C(m, n)

因為ABC與CAB與CBA都是不同的

使用C(m, n)只考慮ABC, 致於怎樣去顛倒替換, 他是不管的