请教GWD-05-Q28

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)

没看懂？

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?

题目意：某个商店只卖2种报纸，A报纸每份1元，B报纸每份1.25元，假设R%的商店收入来自A报纸的收入和P%的报纸卖的是报纸A，求用P来表示R

==因为商店只有2分报纸，那么设商店一共有x份报纸，那么P%x=A报纸的量，（1-p%）x=B报纸的量

收入=A报纸的收入+B报纸的收入

A报纸收入=p%x*1

B报纸的收入=(1-p%)*1.25

所以R%*(P%x*1+(1-p%)*1.25)=p%x*1

换算一下就可以啦。。。