[求助]PREP MATH看不懂题，快考了，急~添加了题目了,大家帮忙啊（已解决）

aliciafull

已经弄明白啦，谢谢各位

[此贴子已经被作者于2008-9-13 19:11:33编辑过]

aliciafull

[attachimg]67343[/attachimg]

刚才没传上来,郁闷

aliciafull

[attachimg]67344[/attachimg]

还有一个,呵呵,双击一下这个图片就会出来清晰的了,先谢过!

aliciafull

up~

aliciafull

怎么没人解答呀，太简单了么。。。

sheibiwosha

第一题，原体如下

On Jane's credit card account, the average daily balance for a 30-day billing cycle is the average (arithmetic mean) of the daily balances at the end of each of the 30 days.  At the beginning of a certain 30-day billing cycle, Jane's credit card account had a balance of $600.  Jane made a payment of $300 on the account during the billing cycle.  If no other amounts were added to or subtracted from the account during the billing cycle, what was the average daily balance on Jane's account for the billing cycle?

 

(1)  Jane's payment was credited on the 21st day of the billing cycle.

 

(2)  The average daily balance through the 25th day of the billing cycle was $540.

意思是J有一张信用卡，信用卡上可以存款，也可以刷，但刷掉的钱不是马上就扣掉，而是在某一天被扣。

卡的balance就是卡上的余额。现在J存了600块在卡上，并刷了300块，当然，这300块不是马上就从卡上扣除的，要求这张卡30天的平均balance，也就是30天balance之和除以30

条件1，如果是在第21天扣除的，那么前20天的balance都是600，后10天都是300，当然能算出30天的balance。

条件2，前25天的平均balance是540，你也可以算出那300块是哪天被扣除的，从而可以知道30天的平均 balance是多少

sheibiwosha

第二题，原体如下

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

谁如下计算：

这个人收入的2%，再加上这个人收入的%1和100元的平均值

那么他的收入是I的情况下，税如下：

0.02I+(100+0.01I)/2

估计你是这句没看懂：average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income

100 units of Country R's currency 是说这个国家货币的100单位，中国的话就是100人民币，美国就是100刀了

aliciafull

谢谢sheibiwosha，终于弄明白了~
再贴一道题

    

At
least 100 students at a certain high school study Japanese. If 4 percent of the
students at the school who study French also study Japanese, do more students
at the school study French than Japanese?

    

(1)
16 students at the school study both French and J

    

(2)
10 percent of the students at the school who study J also study F.    B

这种类型的题，我都不太会。。。请教

cypolo

以下是引用aliciafull在2008-9-13 17:16:00的发言：
谢谢sheibiwosha，终于弄明白了~
再贴一道题

 

At
least 100 students at a certain high school study Japanese. If 4 percent of the
students at the school who study French also study Japanese, do more students
at the school study French than Japanese?

 

(1)
16 students at the school study both French and J

 

(2)
10 percent of the students at the school who study J also study F.    B

这种类型的题，我都不太会。。。请教

这一题我一开始也想了半天，凭感觉是E呢，但后来想了想，在草稿纸上画了个图就解决了！

图你就这样画：

1.两个相交的圆（一大一小），一个是J一个是F；

2.如题意，相交的部分如题干所述，代表了4%的 “study French also study Japanese”；

3.再如条件1，这个相交部分代表了16个人，不难发现这个条件没用；

4.再如条件2，这个相交部分代表了“10 percent of the students at the school who study J also study F”；

5.综上，通过对相交部分的比较，可以发现这个部分代表的是圆J的10%，和圆F的4%

注意！study French also study Japanese 和 study J also study F 是两个概念，这个对最后比较两个圆的大小起决定作用

aliciafull

谢谢cypolo，画图的确是好方法，开始我也画了，可是没把条件想明白，这次弄懂了~