A man walks into a store, steals a $100 bill from the register, and leaves. But the story doesn’t end there. He soon returns, uses that same bill to buy $70 worth of goods, and receives $30 in change. The question sounds simple: how much has the store actually lost?

At first, some people argue that the loss is $200. After all, the thief took $100 from the register, then walked away with merchandise worth $70 and another $30 in cash. Others insist the loss is only $100 because the stolen bill eventually made its way back into the register. The trick is understanding how the two transactions fit together.

When the thief returns the stolen bill as payment, the store gets its original $100 back. But in exchange, it hands over $70 worth of merchandise and $30 in change. The returned bill balances the cash that was initially stolen, but the goods and change are now gone.

Add those two amounts together, and the answer becomes clear: the store lost $100 in total—$70 in merchandise and $30 in cash.

The riddle is a reminder that a confusing-looking transaction can become much easier when you track what actually leaves the store and what comes back. The stolen bill is counted only once, and the final loss is the value of what the thief takes away.