A librarian bought some story books for children for Rs 2000. Had the price of each book reduced by Rs 10, he would have bought 10 more books. Find the ORIGINAL price of each book.

Let the number of books bought be x and price of each book be Rs p.

∴xp = 2000.....(1)

According to the question, if the price of each book is reduced by Rs 10, he would have bought 10 more books.

∴(x + 10)(p - 10) = 2000

⇒xp + 10p - 10x - 100 = 2000

⇒10p - 10x = 100  (From equation (1))

⇒p - x = 10.....(2)

As price can not have a negative value, 

∴Original price of each book = p = Rs 50