GMAT Pre Math 题求助!!

Snazzy

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 B, 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)

Thank you

boussoler

我算出来的答案跟选项都对不上。。。
假设卖出去n分，n(1-p)*1.00是a的收入
b的收入是n*p*1.25
我们知道r是a的总收入百分比, 哪么b占1－r
所以，（1-r）/r＝n*p*1.25／n(1-p)*1.00
r=(1-p)/(0.25p+1)
cc...结果跟答案相差甚远！
可是我没觉的思路有错误，请指点

emma-maple

假设Ａ报卖出Ｘ份，Ｂ报迈出Ｙ份，根据条件知道：

R/100=1X/1X+1.25Y

P/100=Y/X+Y

得不出答案啊！

hebbechou

题目的意思是＂上周日某商店卖报纸．Ａ报每份卖１元，Ｂ报每份卖１．２５元．除此以外，没有卖别的报纸．如果百分之Ｒ的营业额来自于卖Ａ报所得，Ｂ报卖出的份额占到百分之Ｐ的话，下面哪个能正确的用Ｐ表示出Ｒ？

karen_gao

假设该店卖出Newspaper A的数量为A，卖出newspaper B的数量为B，则有：

r%(A+1.25B)=A,

P%(A+B)=B;

然后应该就可以得出答案了，我就不具体算了。