🔞 ADULT: Article/christmas math puzzle - High Quality

I’ve been out of school for decades, and I don’t spend my days solving equations (I’m more of a word person). Still, I like to think I have a solid grip on basic math: I can usually gauge whether a sale price is actually a deal. I know how to split a dinner bill without using the calculator app. And I’m perfectly capable of justifying questionable purchases with highly sophisticated mental accounting.

Yet every so often, a supposedly “easy” math problem explodes across social media and stops me in my tracks. The numbers are small. The steps seem obvious. But the comment section is full of confident adults insisting on completely different answers. That’s usually the moment I start questioning whether my grasp on basic math is as firm as I thought.

So what’s going on here? Is the problem genuinely tricky, or are we collectively overthinking something simple? To find out, I asked Ben Orlin, a math educator, writer and the creator of Math with Bad Drawings, to walk me through one of these viral tricky math problems—and explain why it manages to confuse so many people. Keep reading as we run the numbers.

Get Reader’s Digest’s Read Up newsletter for more puzzles, humor, travel, tech and fun facts all week long.

What’s the viral math puzzle?

You’ve no doubt seen some version of this viral math problem making the rounds on Facebook, Reddit or X (though we’ve given it a seasonal twist):

Santa bought a reindeer for $800.

He sold it for $1,000.

He bought it again for $1,100.

He sold it again for $1,300.

How much money did Santa earn?

At first glance, it seems simple enough. And yet it’s exactly the type of riddle that sparks endless debate online. That’s not an accident: Math puzzles like this are carefully constructed to trip people up, which is why arguing in the comments is so irresistible.

How do you solve the math puzzle?

According to Orlin, the key to solving the problem is to set aside the storytelling details that distract from the math. “I look at this as two sales—ignoring the fact that the two items are the same,” he explains.

In the first transaction, Santa buys the reindeer for $800 and sells it for $1,000, resulting in a $200 profit.

In the second transaction, Santa buys the reindeer for $1,100 and sells it for $1,300, making another $200. “Overall, he netted $400,” Orlin says.

Seen this way, the problem becomes much simpler: Each buy-and-sell cycle stands on its own, and the total profit is just the sum of those two gains.

Why are so many people getting this one wrong?

Scroll through the comments on any post featuring this problem, and you’ll see a wide range of answers. Some people insist Santa made $200. Others confidently argue the answer is zero, claiming he “ended up where he started.” A few even land on $500 or $600, usually by adding up all the numbers without clearly defining what counts as profit.

According to Orlin, these mistakes aren’t random: They stem from how chaotic the story feels. “This question is like a game of three-card monte, money flying this way and that,” he says. “It’s understandable that some of us find it hard to keep track.”

One common wrong approach is to focus on the reindeer itself rather than the transactions. People mentally track whether Santa owns the reindeer at the end, then reason backward from there. Others try to collapse the entire story into a single calculation—subtracting the first purchase price from the final sale price—without accounting for the fact that Santa had to buy the reindeer twice.

Another frequent misstep is mixing profits and expenses into a single running total without resetting between transactions. The repeated buying and selling create the illusion that earlier gains somehow cancel out later ones, even though each sale generates its own profit.

In short, the problem overwhelms people with movement. When money changes hands multiple times, it’s easy to lose sight of the underlying structure. Strip the story down to two separate buy-and-sell events, and the confusion disappears. But as Orlin points out, “when you’re translating a word problem into arithmetical operations, you do need to think about what you’re doing.”

What do problems like this say about the state of mathematics education?

“The standard move is to blame math education,” Orlin says, “but as a math educator, I wish to scapegoat something else: the increasingly digital way that we handle money.”

He points out that people today rarely have to manually track cash the way they once did. “I speculate that any 19th-century shopkeeper, even one with little formal education, would get this question right,” Orlin explains. “Back then, making change and keeping track of expenditures was how you made your daily bread.”

In contrast, modern life is filled with credit cards, automatic payments and invisible transactions. “Money flies this way and that,” Orlin says. “We’re not as practiced at carefully tracking its movements.”

For Orlin, that gap has serious implications. He sees viral math puzzles like this as a warning sign for financial literacy. “If you can’t track the money entering and leaving your pocket,” he says, “then cruel and clever people will rob you blind. Math education should, at a minimum, prepare you to fight them off.”