请教NN们一道数学题

maggie88421

请NN们帮忙解答一下这道题，我完全被绕进去了！万分感谢！

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)

zzhGGforever

先由后个条件，卖的报纸中p%是B,A就是1-p%.乘上对应单价，A是1-p%,B是1.25p%,r表示销售额中A的分量，所以r=（1-p%)/(1-p%+1.25p%)=(400-4p)/(400+p).

所以。。。老大您的题目再确认确认

maggie88421

刚才对了两个版本的GWD，答案确实是D.

zzhGGforever

题目前后条件都应该指A吧。。。汗了，你的题目抄错了

zzhGGforever

p%/(p%+(1-p%)*1.25)=D

maggie88421

呵呵！总算是看明白了。谢谢！