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问俩到PREP~NN进来指点!

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楼主
发表于 2009-8-8 07:16:00 | 只看该作者

问俩到PREP~NN进来指点!

1.for any positive integer n, the length of n is defined as the number of prime factors whose product is n. For example,  the length of 75 is 3, since 75=3*5*5. how many two-digit positive integers have length 6?

A.none

B.one

C.Two

D. three

E.four

答案是C。我想6个不同质因子组成的2位数不存在啊?肯定超过100了。就选了A..望NN解答

2. Some of the students erolled at College T are part-time students and the rest are full-time students. By what percent did the number of full-time students enrolled at College T increase from the fall of 1999 to the fall of 2000?

1.There were 50 more full-time students enrolled at College T in the fail of 2000 than in the fall of 1999

2.The total number of students enrolled at College T increased by 5 percent from the fall of 1999 to the fall of 2000

我选了B。答案是E,B难道不能单独决定么?。。

沙发
发表于 2009-8-8 08:00:00 | 只看该作者
第一题,题目没有说不可以重复,75就是重复的:3*5*5两个5.   2的5次方=32,所以有两个数,两倍的32和3倍的32
第二题:1,全职的增加50人。无法得出结果
        2,所以的学生增加5%。也无法得出全职学生增加的比例
所以E
板凳
发表于 2009-8-8 08:05:00 | 只看该作者
1. 质数: 2, 3, 5, 7, 11, 13,...
2^6=64
换一个3 2^5*3=96
再换一个3 2^4*3^2=144 超了
换一个5 2^5*5=160, 超了
别的更没可能, 只有64和96

2. B不知道parttime和fulltime 的比例
地板
发表于 2009-8-8 08:06:00 | 只看该作者
第一题可以有2^6 和2^5*3这两个啊
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