A simple question about a stolen $100 bill has confused more people than anyone expected. At first, it sounds easy. A man steals $100 from a store register, then returns to the same store and buys $70 worth of goods using that same $100 bill. The cashier gives him $30 in change, and the question becomes: how much money did the store actually lose?
Many people immediately say the store lost $200 because the thief stole $100 first, then took $70 in goods and $30 in change. Others argue the store only lost $100 because the stolen bill came back into the register. That is where the trick begins. The same $100 bill cannot be counted twice as a separate loss once it returns to the store.
The clean way to understand it is simple. The store first loses $100 from the register. Later, the thief gives that same $100 back while buying items. At that moment, the cash part is balanced again, but the store still gives away $70 worth of goods and $30 in change.
So the real loss is $100 total. That loss is made up of $70 in merchandise plus $30 in cash. The stolen bill returning to the register cancels out the original missing cash, but it does not cancel the goods and change the thief walked away with.
This is why the answer surprises people. The store did not lose $200, $170, or $130. It lost exactly $100, even though the situation feels more complicated than it really is.