GWD数学题3道=。=

白菜白菜

The sum of all the integers k such that –26 < k < 24 is

A. 0
B. -2
C. -25
D. -49
E. -51


难道不是C吗=。=答案怎么是D。。我脑子有点糊涂了




Q28:

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day.  If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?

A. 100p / (125 – p)
B. 150p / (250 – p)
C. 300p / (375 – p)
D. 400p / (500 – p)
E. 500p / (625 – p)


答案是D，不是很理解这题的意思




Q34:
Professor Vásquez gave a quiz to two classes.  Was the range of scores for the first class equal to the range of scores for the second class?

(1)    In each class, the number of students taking the quiz was 26, and the lowest score in each class was 70.
(2)      In each class, the average (arithmetic mean) score on the quiz was 85.
    
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


答案是C~

白菜白菜

第一题我瞬间明白了=。=求 2 3题的解释 ~~~

金轩宸

为什么我算出来的第二题是 100p/(125-25p)第三题也不懂 我怎么觉得是E?
同求答案

xxxddd

1/r=(x+1.25y)/100x ,1/p=(x+y)/100x
--->1/r=1/100+1.25*(1/p-1/100)=1.25/p-1/400=(500-p)/400p

xxxddd

第三题没可能啊，随便举个例子{100,70,85……}{90,90,90,70,85……}不就不等么。。

hxd920704

个人觉得第三题少了个条件，应该分数都是整数，没有70.5这种分数，这样就可以推出来85是中位数也是平均数，最高分是95,所以极差就出来了是25

zai

为什么我算出来的第二题是 100p/(125-25p)第三题也不懂 我怎么觉得是E?
同求答案

-- by 会员 金轩宸 (2012/8/8 16:10:04)

这两题我和你算出来都一样，第一反应，同求，PS，楼下的式子没看明白，为什么要1/r？

renyu199014

A的revenue=1*p/100*m(设m为卖出报纸的总数)  注意这里p和r 都是百分数，因而需要在计算是/100或*100
B的revenue=1.25*（100-p）/100*m
r=[1*p/100*m+1.25*(100-p)/100*m]*100
化简以后，r=400p/500-p

第三道同样觉得缺条件吧

xxxddd

x是A的销量，y是B的销量，r=100x/(x+1.25y),p=100x/(x+y),换成倒数，同分母就好计算了。

白菜白菜

嗯嗯 谢谢大家啦。明白了
第三题貌似看了很多版本，答案说是E。可能GWD答案错了吧~！