ong wrote:

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 storeâ€™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 â€“ p)

B. 150p / (250 â€“ p)

C. 300p / (375 â€“ p)

D. 400p / (500 â€“ p)

E. 500p / (625 â€“ p)

Let n = total number of sold

Total revenue R = 1n(p/100) + 1.25n(1-p/100)

R*r/100 = 1n(p/100)

R*r = n*p

[1n(p/100) + 1.25n(1-p/100)]*r = np

[np+1.25n(100-p)]r = 100np

r = 100p/[125-0.25p]

r = 400p/(500-p)

Hence D.

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