answer：
- 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.