A Simple Math Problem That Divides the Internet: Why People Can’t Agree on the Answer

A seemingly simple math problem has sparked widespread debate online, leaving many people surprised by how difficult it is to agree on a single correct answer. The equation in question—20 ÷ 5(2 + 2)—appears straightforward at first glance, yet it has managed to divide opinions across social media platforms, classrooms, and comment sections worldwide.

At the heart of the confusion lies the way people interpret the order of operations. Some arrive at one answer, while others confidently defend a completely different result. This disagreement has led to viral claims such as “only 1 in 10 people can solve this correctly,” reinforcing the idea that even basic arithmetic can become controversial when notation is unclear.

The issue begins with how the expression is written. Most people are taught to follow the order of operations using rules such as PEMDAS or BODMAS—Parentheses (or Brackets), Exponents (or Orders), Multiplication and Division, followed by Addition and Subtraction. According to these rules, operations inside parentheses are performed first, and multiplication and division are then handled from left to right.

Applying this standard method, the expression becomes 20 ÷ 5 × 4, since (2 + 2) equals 4. From there, division and multiplication are performed left to right, resulting in 4 × 4 = 16. Under modern mathematical conventions, this is the correct interpretation.

However, many people instinctively read 5(2 + 2) as a single grouped term, interpreting the equation as 20 ÷ [5 × (2 + 2)], which leads to a different answer. This interpretation reflects older or informal notation practices, where implied multiplication was sometimes treated as having higher priority than division. While this approach feels intuitive to some, it is not consistent with modern standardized mathematical rules.

Mathematicians emphasize that the real problem is not people’s intelligence, but the ambiguity of the expression itself. Without clear grouping symbols, equations like this can easily be misread. In professional mathematics, science, and engineering, such ambiguity is avoided by using additional parentheses or clearer formatting to ensure only one valid interpretation.

This viral debate highlights a broader issue in math education: many people memorize rules without fully understanding why they exist. As a result, when faced with ambiguous notation, confidence can outweigh correctness. It also shows how social media amplifies confusion, turning educational misunderstandings into viral challenges.

Ultimately, this math problem serves as a reminder that clarity in notation matters. While the correct answer under modern conventions is 16, the debate itself reveals more about how math is taught and communicated than about people’s ability to calculate. Sometimes, the lesson is not about the number you get, but about understanding the rules that lead you there.

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Sources

• Khan Academy. Order of Operations Explained.

• Encyclopaedia Britannica. Order of Operations.

• Mathematical Association of America (MAA). Ambiguity in Mathematical Notation.

• National Council of Teachers of Mathematics (NCTM). Teaching Mathematical Reasoning.

• Wolfram MathWorld. Order of Operations and Implied Multiplication.