Loss Due to Fake Notes

A customer in Ramani Watch shop bought a battery for Rs. 12 and paid with a Rs. 20 note. Ramani has no change and walked over to neighboring Kalyani's sweet shop.

A minute after the customer had left, Kalyani stormed into Ramani's store, indignantly waves the Rs. 20 note under Ramani's nose and told her it is counterfeit. Of course, Ramani has to redeem the bill by paying Rs. 20.

Ramani thought "On top of this Rs. 20 loss, I had given Rs. 8 change to the crook who bought the battery. So I lost Rs. 28 altogether".

Was she right or wrong?

Answer to the Puzzle

Ramani was wrong; her damage amounted to only Rs. 20. She paid out to the customer the value of one battery, that is Rs. 12, and Rs. 8 change, and to Kalyani, Rs. 20 altogether Rs. 40; but she also received Rs. 20 in change from Kalyani. Therefore, her loss was only Rs. 20.

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