Question

A shopkeeper buys some books for rupees 80 if he had bought 4 more books for the same amount each book would have cost Rupees 1 less find the number of books he bought​

Answer 1

let shopkeeper buys books = x

total cost = 80

cost of a book = 80/x

according to given condition

(x+4) * (( 80/x) - 1) = 80

(x+4)*(80-1x) = 80x

80x - x2 + 320 - 4x = 80x

-x2 +320 -4x =0

x2+ 4x - 320 =0

x2+ 20x - 16x -320=0

x( x+20) -16 ( x+20) =0

(x+20) (x-16)=0

x= -20 / x=16

A shopkeeper buys 16 books