I’ve been out of school a long time (I mean a long time), yet I think I’m still pretty good at basic math. I’m always able to figure out whether a “bargain buy” at the supermarket is actually a bargain. I’m usually the one calculating the tip and splitting the bill when out to dinner with friends. And, of course, I’m an expert at girl math.
But every now and then, I stumble upon one of those viral math problems circulating on social media, and for a split second, I find myself stumped (especially when I see all the wildly conflicting answers in the comments), and I wonder if I could still pass an elementary school math test.
So is it true that only geniuses can solve this math equation? I reached out to a mathematics professor to help me run the numbers on this tricky math problem.
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What’s the viral math equation?
You’ve no doubt seen this math problem (or one similar to it) making the rounds on Facebook: 4×4-4÷4+4. The equation seems so simple. But math puzzles like this go viral because they’re designed to trip people up—and that’s exactly why they’re so compelling.
How do you solve the equation?
To solve the equation 4×4-4÷4+4 (or any equation for that matter), you need to follow the proper order of operations, the set of rules that determines the sequence in which mathematical operations should be performed. The acronym PEMDAS is a good way to remember the order: parentheses, exponents, multiplication, division, addition, subtraction. And a good mnemonic device to keep that straight is “Please Excuse My Dear Aunt Sally.” Some people even say “Please Excuse My Dear Aunt Sally and Let her Rest,” as a reminder to work on those operations from left to right. (Fun fact: In the U.K. and a few other countries, they use a different acronym, BODMAS—brackets, orders, division, multiplication, addition, subtraction—but it’s the same concept.)
So armed with PEMDAS, I enlisted the help of Alvaro Lozano-Robledo, PhD, a professor of mathematics at the University of Connecticut, who’s known for posting educational math content on his YouTube channel and on TikTok. Here are the steps to solving the viral equation 4×4-4÷4+4.
- Since there are no parentheses or exponents in this expression, start with multiplication and division, working from left to right. So first we do the multiplication: 4×4=16.
- Next, we tackle the division part of the equation: 4÷4=1.
- Then, we move on to addition and subtraction, also working from left to right: 16-1=15.
- Finally, we add the last 4: 15+4=19.
Why are so many people getting this one wrong?
“Math is very clear,” says Lozano-Robledo. “But I can imagine people who have been removed from math for a long time might not remember what goes first.”
A common mistake is people tackling the problem from left to right, with no regard to PEMDAS.
Another common misstep happens when people treat multiplication and division as if they should be done strictly left to right, instead of recognizing that they’re on the same level of priority. The same goes for addition and subtraction—those also need to be handled left to right, not based on which one comes first.
But the main reason people get the wrong answer to this and other viral math equations is that these puzzles are intentionally confusing. “If you write math the right way, everything is crystal clear,” he says.
In this equation, for example, had 4×4 been in parentheses, the fact that one needed to solve that part first would have been obvious. But without those grouping symbols, people misinterpret the structure. “Writing parentheses is free,” Lozano-Robledo jokes. “This is not a telegram we’re sending out that we’re going to be charged per character.”
And it’s not just the structure that adds to the confusion. Lozano-Robledo points out the use of the ÷ symbol in the equation as opposed to the slash (/) for the division element. “We don’t even use that symbol except when you’re trying to be confusing,” he says.
What do mathematicians think of viral equations?
“It’s extremely frustrating to see those equations posed as they are,” Lozano-Robledo says, “because students or people are going to think, If I’m confused about a problem about multiplying and adding 4s, how am I going to be able to do any math whatsoever, especially at a higher level?”
The bottom line, Lozano-Robledo says, is that if you have difficulty solving a viral math equation, don’t blame yourself! “The ones who failed are not the people that got different and wrong answers. The people who failed are the ones who proposed and wrote the problem in a confusing way, when you can always communicate math in a straightforward way,” he adds.
So the next time you come across one of these viral math equations, remember to follow the order of operations carefully. But also remember that these puzzles aren’t about teaching math lessons; they’re designed to grab attention and spark conversation.
About the expert
- Alvaro Lozano-Robledo, PhD, is a professor of mathematics at the University of Connecticut. He posts educational math videos on his YouTube channel and on TikTok. He’s also the author of two books, Number Theory and Geometry and Elliptic Curves, Modular Forms, and Their L-functions.
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