賠了多少?

一個男人從商店偷了100元, 然後用這張百元鈔向該店買了70元的東西, 店老板找30元給男人.

請問, 老板共虧了多少錢?

這很簡單, 但不知道為什麼讀者文摘要解釋那麼多, 答案在下面這一大段英文的下面.

What you’re thinking

Seeing all those numbers being bandied about, you might assume this seemingly short riddle requires some lengthier form of calculation. Indeed, the shop owner has lost $100 right off the bat, but they get that $100 bill back almost immediately.

Of the $100 stolen from him, the shopkeeper keeps only $70, handing back $30 to the thief. Because this transaction results in the shop owner ending up with $30 less in the cash register, you might be thinking that the answer is $30. Or is it the $70 in merchandise that the shopkeeper will have to replace?

Let’s not forget that when all is said and done, the thief walks away with $70 worth of goods. So you might be thinking that the shop owner is down the original $100 plus that $70 worth of goods, adding up to a total loss of $170. Or perhaps it’s that the shop owner is down the original $100 bill plus the $30 in change he handed over at the end? It could also certainly appear that the shop owner has lost a total of $200, which is the sum of the original $100 bill plus the $70 in merchandise and the $30 he handed to the thief as change.

Like all the best math riddles, the answer to this one is not what it seems. In fact, when you get right down to it, it might not even qualify as a math riddle. Or it might be the simplest math riddle ever.

答案是: 100元

The answer

What’s the “man steals $100 from a shop” riddle answer? He has lost $100. It’s that simple. If a man walks into a shop, sidles over to the cash register and, unbeknownst to the shop owner, manages to extract a $100 bill, that’s precisely what the shop owner has lost.