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Algebra
Level
2
If the price of a book is reduced by 5 rupees,a person can buy 5 more books for rs 300 find the original list price of the book?
30
20
-15
15
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1 solution
Being p the original price and x the amount of books you could buy by p with 300 rupees. p×x=300 (I) We were told that reducing the price to p-5, we could buy x+5 books with 300 rupees. (p-5)×(x+5)=300 <=> p×x+5p-5x-25=300 (II) Replacing p×x in (II) by its value in (I), we'll have: 300+5p-5x-25=300 <=> 5x-5p=-25 <=> x-p=-5 <=> x=p-5 (III) Replacing x in (I) by its value I (III), we'll have: p×(p-5)=300 <=> p^2-5p-300=0 => p=[5+sqrt(25+1200)]÷2=(5+35)÷2=20
Therefore, the original price was 20 rupees