Here’s a quick, fun, slightly self-indulgent story: I recently started studying for the GRE, and while flipping through the workbook, I realized I hadn’t taken a math class in almost nine years.
Any confidence I had in my quantitative skills quickly disappeared. I’ve since started watching basic high school math lessons online because I genuinely have to begin from scratch, so when I came across this viral math problem stumping the internet, I thought, “Aha! A chance to test my 9th-grade math skills!”
File that under “famous last words.”
Here’s the situation: researchers in Japan reportedly found this deceptively simple number puzzle after discovering that only 60 percent of people in their 20s who tried it got it right.
(Great, another thing millennials have apparently ruined—math.) Since then, it’s gone viral, as these things tend to do, because it seems none of us can resist a brain teaser we’ll probably fail at.
But maybe there’s more going on than it first appears. The moment I saw it, I suspected there were tricks involved—it looked too easy. I also knew that if I tried to solve it live in this article, I would never be taken seriously again. My math skills are, frankly, terrible. I’d likely be laughed out of grad school, or something close to it.
So instead, I turned to instructional videos online. Because if there’s one thing I’ve learned, it’s that if you’re struggling with something—anything—someone else probably is too, and chances are they’ve already figured it out and filmed it step by step. So yes, I spent the morning watching other people do math. It was… educational.
Now, before you go down the same rabbit hole, you should try the problem yourself. Ready? Here it is:
OK, thoughts? Concerns? Did you get negative one? Did you get nine? Yeah, me too.
But we’re both wrong, and we’re wrong because of an acronym. Apparently, one common way people try to solve this problem is… drumroll, please… PEMDAS.
“PEMDAS, duh!” they say. Surely you remember PEMDAS? Honestly, I don’t think I even knew it to begin with, but it stands for Please Excuse My Dear Aunt Sally—or, in its more practical form, Parentheses, Exponents, Multiplication, Division, Addition, Subtraction, which is the standard order of operations for solving math problems. But not here. Following PEMDAS leads to negative one, which turns out to be wrong.
And negative one isn’t the only incorrect answer. Others were tripped up by the “three divided by one third” part, often overthinking it. They missed that when you write one third as 1/3, the “/” is itself a division symbol. The result becomes this:
This gets you nine. Again—no.
So what’s the correct answer? It’s one. Just plain old one. Here, my sweets, is how you get there: