- Twitter user @pjmdoll shared a math problem: 8 ÷ 2(2 + 2) = ?
- Some people got 16 as the answer, and some people got 1.
- The confusion has to do with the difference between modern and historic interpretations of the order of operations.
- The correct answer today is 16. An answer of 1 would have been correct 100 years ago.
- Visit INSIDER’s homepage for more stories.
Viral math equations have been known to divide people on the internet. Some problems are so mind-bogglingly hard that they seem impossible, even if they’re meant for elementary school students.
This latest viral problem shared by Twitter user @pjmdoll is one such equation.
oomfies solve this pic.twitter.com/0RO5zTJjKk
— em ♥︎ (@pjmdolI) July 28, 2019
The equation is: 8 ÷ 2(2 + 2) = ?
Everyone keeps getting different answers.
i have 2 math degrees it’s 1
— laur♏️ (@lauram_williams) July 30, 2019
16… this is embarrassing for some of y’all
— becca 10✧*.✰LILY + BARBS DAY (@spaceywhy) July 30, 2019
notation y’all pic.twitter.com/yAMie100Hi
— maggie (@BatmanOfficial_) July 29, 2019
In PEMDAS multiplication and division take equal priority so you do whichever is first from left to right. Same for addition and subtraction. pic.twitter.com/1617gChUms
— George W. Kush (@supermaddd) July 29, 2019
Remember a(b+c)=ab + ac and it is law of distribution in mathematics.
Where PEMDAS is not a law, it is just a way to help us memorize things, we can use pemdas only after using all math laws to simplifying all steps first.
— Light???? ᴮᵃⁿᵍᵗᵃⁿ ᶠᵒʳᵉᵛᵉʳ ???? (@SakuraTsukimine) July 29, 2019
Here’s the correct way to solve 8 ÷ 2(2 + 2) = ?
First, add the numbers in the parentheses.
8 ÷ 2(4) = ?
Now, do the multiplication and division from right to left.
8 ÷ 2(4) = 4(4) = 16.
The confusion is caused by the difference between modern and historic interpretations of the order of operations, known as PEMDAS:
- Multiplication and Division (left to right)
- Addition and Subtraction (left to right)
A similar math problem went viral in 2011, when people couldn’t agree on the answer to 48÷2(9+3). Presh Talwalker, the author of “The Joy of Game Theory: An Introduction to Strategic Thinking,” explained the controversy on his YouTube channel MindYourDecisions and in a post on his blog.
People who got the number 1 as the answer to this problem were using an outdated version of the order of operations, multiplying 2(4) first and then dividing 8 by 8, according to Talwalker. That answer would have been correct 100 years ago. But plugging the equation as is into a modern calculator results in an answer of 16. You have to add another set of parentheses to get an answer of 1.
- Talia Lakritz/INSIDER
Talwalker explains that part of the confusion is also caused by how the division symbol is ambiguously set in the problem.
“Textbooks always have proper parentheses, or they explain what is to be divided,” he writes on his blog. “Because mathematical typesetting is much easier today, we almost never see ÷ as a symbol, and instead fractions are written with the numerator vertically above the denominator.”
You can watch Talwalker’s full explanation of that equation below.