1.Tokeepcomputerfilessecure,manyprogramsrequiretheusertoenterapassword.Theshortestallowablepasswordsaretypicallysixcharacterslongandcancontainbothnumbersandletters.Howmanysix-characterpasswordsarepossibleif(a)characterscanberepeatedand(b)characterscannotberepeated?
2.Arelayracehas4runnerswhorundifferentpartsoftherace.Thereare16studentsonyourtrackteam.Inhowmanywayscanyourcoachselectstudentstocompeteintherace?
3.Yourschoolyearbookhasaneditor-in-chiefandanassistanteditor-in-chief.Thestaffoftheyearbookhas15students.Inhowmanywayscanstudentsbechosenforthese12positions?
4.Auditionsarebeingheldfortheplayshown.Howmanywayscantherolesbeassignedif(a)6peopleauditionand(b)9peopleaudition?看下面给的信息.
Partsavailable:
studentA,studentB,Principal,Teacher,Librarian,Coach
第1题和第4题有2个小问题,都要回答,