11. A man bought a certain number of articles for $300. He sold all of them at $15 for a package of 4. If the total profit he made is the same as the original cost of 25 articles, how many articles did he buy?
answer:100
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f4 maths(1)
2007-10-08 5:17 am
回答 (1)
2007-10-08 5:25 am
✔ 最佳答案
Let x be the articles that he bought.Cost of 1 article = 300/x
Total selling price = 15x/4
Profit = 15x/4 - 300 = 25*300/x
Hence 15x/4 - 300 = 7500/x
15x^2 - 1200x = 30000
x^2 - 80x - 2000 = 0
(x-100)(x+20) = 0
x = 100 or -20 (rejected)
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