请教一道数学题

magicgirl2708 · 发表于 2010-8-22 00:15:48

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)

ANS：D

菜鸟提问，请多包涵

luyuan182 · 发表于 2010-8-22 00:26:31

根据题目提示列式：
A的销售额百分比=r%=A的销售额/总销售额=1*P%/[P%+1.25(1-P%)]
把上面的式子简化了就是答案D

请教一道数学题

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