此题如何解的？

james2201

Last Sunday a certain store sold copies of Newspaper Afor $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 ofnewspaper B, which of the followingexpresses 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)


Answer: D

gdboy8888

Last Sunday a certain store sold copies of Newspaper Afor $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 ofnewspaper A, which of the followingexpresses 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)

我算了好久没算出答案，百度了一下，发现楼主你打错了。。。
设总报纸数目w
A: 单价$1；数量M=pw/100
B: 单价$1.25；数量N=(100-p)w/100
-----→
带入 r(M*1+N*1.25)/100=M*1  化简即可

james2201

题是从文件C+P过来的，不过我真没想过可能是题本身有问题

谢谢帮助