这几道题都是关于数学哪方面知识的?
1.Anurncontainssixred,threewhite,andtwobluemarbles.Inhowmanywayscanthreemarblesbeselectedsothatatleastoneisblue?
2.Amanhasapenny,anickel,adime,aquarter,andahalf-dollarcoininhispocket.Themanreachesintohispocketandselectsthreecoins.Howmanydifferentsumscanhethreecoinsform?
3.Fivecardsaredrawnfromastandarddeckof52cards.Howmanydifferenthandsoffivecardscontainfourofakind(fourcardsofthesamerankplusoneadditionalcard)?
4.Anicecreamstorehas31flavorstoselectfrom.Acustomerwantstoselecttwodifferentflavors.Howmanywayscanthecustomermakethisselection?
5.Asetcontainsfiveelements.Howmanysubetscanbeformedfromtheset?