Question

A child purchases a number of notebook for rs 80. If he had purchased 4 more notebooks for the same amount from the other bookseller , then a notebook would have cost rs 1 less. Represent the above situation in the form of quadratic equations .

Answer 1

1)let each book cost = Rs x
number of books purchased = n
total cost = Rs 80
xn = 80
n= 80/x---(1)
2) if he purchased 4 more books
number of books = n+4
cost of each book = Rs(x-1)
total cost = Rs 80
(x-1)(n+4) =80
(x-1)(80/x +4)=80 from (1)
(x-1)(80+4x)/x=80
(80x+4x²-80-4x)=80x
4x²+80x-80-4x-80x=0
4x²-4x-80=0
divide each term with 4
x²-x-20=0