A man sells a book at a profit of 20%. If he had bought it at 20% less and sold it for ₹18 less, he would have gained 25%. The cost price of the book is:

Answer 1

We know two things about the cost of the book (C) and the profit (P) from it

It sold at a 20% profit, or P = 1.20 C

It would sell at a 25% profit if the cost were reduced by 18ϒ or P = 1.25 (C - 18ϒ)

Since the profit is common to both equations, the two can be set equal to each other by the substitution rule:

P = 1.25 (C - 18ϒ) = 1.20 C

1.25C - 22.5ϒ = 1.20C

0.05C = 22.5ϒ



C = 450ϒ