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,