Example 1 — Expand a product
EasyProblem
Use distribution to compute .
Solution
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A factor multiplies a sum, so distribute it over each term.
Name the structure before touching arithmetic — that is what makes the right method obvious.
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Ask the recognition question: Is a single factor multiplying a sum where it must reach every term inside?
If the answer is yes, the concept applies; the cue, not a keyword, decides the method.
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Multiply 3 by each term: .
The rule is chosen only after the structure matches, so the steps mean something.
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Keep units, shape, or answer form tied to the story so the work does not become symbol pushing.
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Check the answer against the original question.
It should fit the mental model — the factor reaches every term inside. If it does not, revisit the recognition step before changing the arithmetic.
Answer
18
Takeaway: The factor multiplies every term in the sum, then you add.