A man can purchase a certain number of notebooks for Rs. 300. If the price of each notebook increases by Rs. 5, he would be able to buy 10 fewer notebooks for the same total amount. What is the original price of each notebook?

Explanation

Let the original price per notebook be Rs. x, and the number of notebooks he can buy be y. Then, xy = 300, so y = 300/x. When the price increases by Rs. 5, the new price is (x + 5), and the number of notebooks he can buy is (y - 10). The total cost remains Rs. 300, so (x + 5)(y - 10) = 300. Substituting y = 300/x, we get (x + 5)(300/x - 10) = 300. Simplifying leads to the quadratic equation x^2 + 5x - 50 = 0. Solving this, the positive root is x = 10. Therefore, the original price of each notebook is Rs. 10.