A lady enters a shoe store and buys some shoes that cost 30 euros. The woman pays the clerk with a 50-euro bill but the seller, who has just opened the store, has no change to give her so she leaves the shop next door where they change her 50-dollar bill for 5-dollar bills. The seller delivers the change to the lady and she leaves the store.
After a while, the saleswoman from the store next door enters and tells our salesman that the ticket he gave her was false. How it is impossible to locate the woman and therefore can not recover the money or shoes, the seller exchanges the fake 50 euro bill for another legal tender and apologizes.
After all this, how much money has the seller lost?
The seller lost 50 euros in total. The 50 euros that the shop assistant of the next store changed, finally returned, so this transaction does not affect the total amount of the loss. The seller was finally left with 50 false euros representing the total loss.