Arun
Last Activity: 6 Years ago
Dear student
let the price of one book = x
and the no of book that can be purchased with x rs per book = y
now
x* y = 800
(x –10)(y + 4) = 800
now
xy +4x –10y –40 = 800
put xy = 800
800 + 4x – 10y –40 = 800
4x – 10y = 40
put y = 800/x
then a quadratic equation will be formed in x
solve that equation and you will get the cost of one book.
Regards
Arun (askIITians forum expert)