UC知道4道英文的数学题，请教下高人怎么做？
来源：百度知道 编辑：UC知道 时间：2024/05/21 12:00:21
1.To keep computer files secure, many programs require the user to enter a password. The shortest allowable passwords are typically six characters long and can contain both numbers and letters .How many six-character passwords are possible if (a)characters can be repeated and (b) characters cannot be repeated?
2.A relay race has 4 runners who run different parts of the race. There are 16 students on your track team. In how many ways can your coach select students to compete in the race?
3.Your school yearbook has an editor-in-chief and an assistant editor-in-chief. The staff of the yearbook has 15 students. In how many ways can students be chosen for these 12 positions?
4. Auditions are being held for the play shown. How many ways can the roles be assigned if (a) 6 people audition and (b)9 people audition? 看下面给的信息。
Parts available:
student A, student B, Principal, Teacher, Librarian, Coach
第1题和第4题有2个小问题，都要回答，
麻烦高手写下做题的步骤，谢谢
2.A relay race has 4 runners who run different parts of the race. There are 16 students on your track team. In how many ways can your coach select students to compete in the race?
3.Your school yearbook has an editor-in-chief and an assistant editor-in-chief. The staff of the yearbook has 15 students. In how many ways can students be chosen for these 12 positions?
4. Auditions are being held for the play shown. How many ways can the roles be assigned if (a) 6 people audition and (b)9 people audition? 看下面给的信息。
Parts available:
student A, student B, Principal, Teacher, Librarian, Coach
第1题和第4题有2个小问题，都要回答，
麻烦高手写下做题的步骤，谢谢
都是概率论的题目
1.字母不分大小写，则（1）36^6 六位长度的密码，每位可以取36种不同的字符，六个36相乘（2）36×35×34×33×32×31同样的道理，也可以表示成36!/30!，另一种计算方式是36C6×P6即为从36个字符中任意取6个，然后再乘以6的全排列（书面写法应该是36是C的下标，6是C的上标都在C右边，6是P的下标在右边）
若字母分大小写，则为62^6；62C6×P6即为62*61*60*59*58*57
2.16*15*14*13，四个不同的赛道，第一个可以从16人中任取，有16中选择，第二个可以从剩下的15人中任取15种选择...将结果相乘。其实道理同1.(2),也可写成16C4*4!
3.题目好像有点问题,一个主编一个主编助手哪来十二个职位啊
4.(a)P6，或6!即六个人全排列
(b)9*8*7*6*5*4道理同上，只是，剩下的三个人干嘛去，当观众么？