I love a good riddle, especially one that makes you scratch your head and rethink your basic math skills. Recently, I stumbled upon a brain teaser on Reader’s Digest that had me double-checking my mental arithmetic more times than I’d care to admit. The riddle goes something like this:

A man walks into a shop and steals a $100 bill. He then uses that stolen $100 bill to buy $70 worth of goods. The shop owner, none the wiser, gives him $30 in change. So, here’s the million-dollar question (well, in this case, the $100 question): How much money did the shop owner lose?

At first glance, you might think, “Okay, he stole $100, spent $70, and got $30 back. That means the shop owner lost $100, right?” But then you start overthinking it. You wonder if the $70 worth of goods plus the $30 change should somehow factor into the total loss. You might even question your sanity a bit. I know I did.

Let’s break it down together and solve this sneaky little puzzle. The riddle is not just about theft and purchase; it’s a classic example of a situation where keeping track of money gets tricky. Here’s why it’s so easy to get tangled up in the numbers.

First, let’s consider the initial act: the man steals a $100 bill from the shop. That’s straightforward enough. The shop owner is now out $100. That part is crystal clear. The confusion usually starts with the next step: the thief uses that stolen $100 bill to buy $70 worth of goods.

Now, here’s where our mental math can start to trip us up. When the thief uses the stolen $100 bill, it might seem like the shop owner is losing more money because he’s handing over merchandise. But let’s take a step back. The goods are valued at $70, but the thief doesn’t actually hand over any of his own money; he’s using the shop’s stolen $100 bill.

When the shop owner gives him $30 in change, it feels like there’s another layer of loss. Some might think, “He’s losing $100 plus another $30, that’s $130!” Others might argue, “No, it’s $70 worth of goods plus $30 change, so it’s only $100.” And then there’s the camp that says, “Wait, he stole $100 and then spent $70, so the loss is $170!”

Let’s get our heads straight: The shop owner originally lost $100 when the thief pocketed the bill. That’s our starting point. The moment the thief buys $70 worth of goods, he is just using the already stolen $100. The exchange of goods is neutral in terms of monetary loss because the shop owner still operates within the stolen amount. He hasn’t gained anything back, nor has he lost more at this point – the theft loss stands still at $100.

The confusion gets compounded when the shop owner gives the thief $30 in change. Here’s the critical part to understand: the $30 change doesn’t add an additional layer of loss. It’s part of the $100 that was originally stolen. When the thief walks away with $70 worth of goods and $30 in change, the total loss to the shop owner is $100. He never got his stolen $100 back and lost goods and change equivalent to that amount.