A young girl purchases a book from a shopkeeper and gives him a 100 dollar bill for payment.

The cost of book is 30 dollars but the shop keeper had no change, so he ran next door to get change for the hundred from the next shop. He came back and gave her 70 dollars change.

After some time the next shopkeeper comes with the 100 dollar bill and told the shop keeper that the bill was counterfeit, so he takes his money back. How much money did the original shop keeper lose?

100 dollars

Yes $100 if he gave 100 to the shopkeeper next door and the $30 book cost – total $130

I think he is 70$ down and a book! The girl is 70 up and the second shopkeeper is even.

100 dollars is correct Anant.

You are today’s winner.

That is of course assuming that the shopkeeper sold the book at zero profit.