Question

If. the price of a book is reduced by 5 rupees, a person can buy 5 more books for rupees 300 . find the original price of the book

Answer 1

let the prize of one book be Rs. x

let the no. of books be y

so total amount spent = xy

300 =xy

now changed price of book = Rs. (x -5)

no. of books bought = y + 5

so total amount spent = (x - 5)(y + 5)

300 = xy +5x -5y -25

325 = 300 + 5(x - y)

25 = 5(x - y)

x - y = 5

y = x - 5

now putting this in xy = 300

(x - 5)x = 300

x2 -5x - 300 = 0

x2 -20x + 15x -300 = 0

(x - 20) ( x + 15) = 0

x = 20 or x = -15

Price of book cannot be negative so x is not equal to -15

so actual cost of book is x= Rs. 20