Viral math equations frequently spark lively debates across social media platforms. The confusion usually stems from misapplying the standard order of operations—commonly remembered by acronyms like PEMDAS or BODMAS—which dictates the exact sequence required to solve arithmetic expressions correctly.
In the printed image above, the challenge states: “What is the correct answer to this question. Answer is NOT 21. $20 + 20 \div 10 \times 2 = ?$“. In this guide, we break down the correct mathematical steps to solve the expression accurately.
Step-by-Step Order of Operations (PEMDAS/BODMAS)
+--------------------------------------------------------+
| Order of Operations Map |
+---------------------------+----------------------------+
|
v
+--------------------------------------------------------+
| Step 1: Division | Step 2: Multiplication |
| - 20 ÷ 10 = 2 | - 2 × 2 = 4 |
+---------------------------+----------------------------+
| Step 3: Addition | |
| - Combine 20 + 4 | |
| - Final Result = 24 | |
+--------------------------------------------------------+
1. Perform Division & Multiplication (Left to Right)
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Division: Working from left to right, perform $20 \div 10$ first, which equals $2$.
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Multiplication: Next, multiply that result by $2$: $2 \times 2 = \mathbf{4}$.
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Intermediate Expression: The equation simplifies to $20 + 4$.
2. Perform Addition
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Final Step: Add $20$ and $4$ together: $20 + 4 = \mathbf{24}$.
Order of Operations Summary Table
| Step | Operation | Portion of Equation | Calculated Result | Simplified Expression |
| Start | Original Equation | $20 + 20 \div 10 \times 2$ | — | $20 + 20 \div 10 \times 2$ |
| Step 1 | Perform Division | $20 \div 10$ | 2 | $20 + 2 \times 2$ |
| Step 2 | Perform Multiplication | $2 \times 2$ | 4 | $20 + 4$ |
| Step 3 | Perform Addition | $20 + 4$ | 24 | 24 |
Why People Incorrectly Get 21 or Other Answers
Common mistakes happen when people misapply the order of operations:
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Strict Left-to-Right Evaluation: Adding $20 + 20 = 40$, then $40 \div 10 = 4$, then $4 \times 2 = 8$.
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Doing Multiplication Before Division: Multiplying $10 \times 2 = 20$ first, then $20 \div 20 = 1$, and finally $20 + 1 = 21$ (which is why the puzzle explicitly warns that the answer is NOT 21).
By adhering strictly to standard order of operations rules where multiplication and division have equal priority and are evaluated left-to-right, the correct answer is unambiguously 24.
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Conclusion
Following standard arithmetic rules, the equation $20 + 20 \div 10 \times 2$ simplifies to $20 + 4$, yielding the correct final answer of 24.
Did you solve it correctly on your first attempt? Let us know in the comments below!
FAQ Section
Why isn’t the answer 21?
To get 21, you would have to multiply $10 \times 2$ before dividing $20 \div 10$. However, division and multiplication have equal precedence and must be solved from left to right as they appear.
What does PEMDAS stand for?
PEMDAS stands for Parentheses, Exponents, Multiplication and Division (left-to-right), Addition and Subtraction (left-to-right).
