问几道Prep上的数学,居然错了7个,晕

figoliuxi

 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 ?
    

 

    

(A) 50+I/200

    

(B) 50+3I/100

    

(C) 50+I/40

    

(D) 100+I/50

    

(E)  100+3I/100

(C)

Of the 75 houses in
a certain community, 48 have a patio. 
How many of the houses in the community have a swimming pool?

                

 

                

(1) 38 of the
houses in the community have a patio but do not have a swimming pool.

                

 (2) The number of
houses in the community that have a patio and a swimming pool is equal to the
number of houses in the community that have neither a swimming pool nor a
patio.

(B)

The positive
integer k has exactly two positive prime factors, 3 and 7.  If k has a total of 6 positive factors,
including 1 and k, what is the value of k ?

                    

 

                    

(1) 3² is
a factor of k.

                    

 (2) 7² is not
a factor of k.

(D)

这几个题,我百思不得其解阿.....大家帮哈忙嘛...

figoliuxi

希望有人能解答下,谢谢

pinpin117

The positive integer k has exactly two positive prime factors, 3 and 7.  If k has a total of 6 positive factors, including 1 and k, what is the value of k ?

(1) 3² is a factor of k.

 (2) 7² is not a factor of k.

(D)

根据题意：k has a total of 6 positive factors可以得出，

K=3^2*7和K=3*7^2...两种形式。（2+1）*（1+1）=6

然后可以发现（1）（2）单独分别充分。能够确定K的具体组成。所以D。

pinpin117

Of the 75 houses in a certain community, 48 have a patio.  How many of the houses in the community have a swimming pool?

(1) 38 of the houses in the community have a patio but do not have a swimming pool.

 (2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.

(B)

根据题目假设have a patio为P,have a swimming pool为S，have a patio and a swimming pool 为X，have neither a swimming pool nor a patio为Y。

然后列式：P+S-X+Y=75.

然后根据（2）知道X,Y相等。所以可以把X,Y相抵。

则可以知道：S=75-P=75-48=27.

figoliuxi

谢谢LS两位啊,感觉今天下午做数学状态不好,很急...错了7个,居然还有50...

第一个题有人解嘛?看不懂什么意思啊????

pinpin117

以下是引用figoliuxi在2009/7/30 18:32:00的发言：
谢谢LS两位啊,感觉今天下午做数学状态不好,很急...错了7个,居然还有50...

第一个题有人解嘛?看不懂什么意思啊????

不客气~~~

第一题我也理解不了，尤其是这句话add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency

很困惑~~~呼唤大牛解答！！！help~~~~~

figoliuxi

我当时做这个的时候就估计进入高分题库了,结果后面错了5`6个,晕哦,就是他把我的思维都打乱了....

dabobowa1111

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 ?
    

这道题是很简单的，估计楼主就是读题没读懂啦

题意：在简化之前，R国的收入税是这样计算的，2%的收入+100个R国货币和1%收入的平均值

那么列算式：0.02*I+(100+0.01*I)/2;

就是C了

figoliuxi

确实挺简单的,谢谢LS哈,,唉,,add to结构罢,就被中间and搅浑了....