prep又出两道难题！！

tiya_1125

1. For a certain set of n numbers, where n>1, is the average(arithetic mean) equeal to the median?
(1) if the n numbers in the set are listed in increasing order, then the difference between ant pair of success numbers in the set is 2.

(2) The range of the n numbers in the set is 2(n-1).

我选的是c, 答案是a


2. Before being simplified, the instructions for computing income tax in country R were to add 2% of one' s annual income to the average ( arithetic mean) of 100 units of country R's currency and 1% of one's annual income. Which of the following represents the simplified formular for computing the income tax in country R's currency, for a person in that country whose annual income is I?

A. 50+ i/200   B. 50+ 3I/100   C. 50+ I/40   D. 100+ I/50   E. 100+ 3I/100
这道题我不会做，答案是c

请大家帮着解答一下！！

charlesyang

第二题：2/100*i+（100+1/100/i)/2=1/40*i+50
所以这题应该选C。

育空

第一题没看明白什么是“ant pair of success numbers ”

第二题，t=I*2%+[(100+I*1%)/2]=50+I/40

yougushizi

第一题，1）包含2）因为根据条件1），a(n)=a(1）+（n-1）d，且是升序排列，d=2,那么：最大数-最小数=a(n)-a(1)=2(n-1)
so 有1）即可。
至于条件一，可以知道mean=a(1)+(n-1),如果n是奇数，median是第(1+n)/2个数 ，即a(1)+(n-1);如果n是偶数，median 是n/2和n/2+1两个数的平均数，仍是a(1)+(n-1)


第二题，我没看懂题，请达人过来断个句……

yougushizi

明白了，谢谢Charles
2%的此人工资，加上（100元该国货币和1%这人工资）的平均数。
too tricky in the description....

第二题：2/100*i+（100+1/100/i)/2=1/40*i+50
所以这题应该选C。

-- by 会员 charlesyang (2010/8/7 10:00:39)

yougushizi

I guess "ant: should be "any"任何连续两数之间差2

第一题没看明白什么是“ant pair of success numbers ”

第二题，t=I*2%+[(100+I*1%)/2]=50+I/40

-- by 会员 育空 (2010/8/7 10:05:27)

anniebieb

楼主请问prep有数学破解版的吗？？ 谢谢！！！！！