几道GRE数学题1.In a series of races,10 toys cars are raced,2 cars

问题描述:

几道GRE数学题
1.In a series of races,10 toys cars are raced,2 cars at a time.If
each car must race each of the other cars exactly twice,how many races must be held?
2.The daily rate for a hotel room that sleeps 4 people is $39 for one person
and x dollars for each additional person.If 3 people take the room for one day
and each pays $21 for the room,what is the value of
3.What fraction of the positive intergers that are multiples of 30 and are less than or equal to 360 are multiples of 12?
答案为1/2
1个回答 分类:英语 2014-10-03

问题解答:

我来补答
第一个题是排列组合的题,是说十辆车比赛,每次两辆车一起比赛,问如果每辆车需要和其他的每辆车比赛两次,需要举行多少次比赛.可以先考虑每辆车和其他的车各比赛一次,也就是10*9/2,在乘以2就是比赛两次的总场数啦~(组合的那个符号打不出来,就直接写的算法啦),你可以复习一下排列组合的问题,不过一般不会出太多这样的题.
第二题暂时没太明白,
第三题是说问在小于等于360的范围里,30的倍数的个数是12的倍数的个数的几分之几.(我的理解,你可以算一下,不过我怎么感觉不是这答案呢.)
 
 
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