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Rule of Three
Solve proportions fast. If 3 apples cost $2, how much are 10?
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corresponds to
corresponds to
Enter A, B, and C to solve for X.
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About the Rule of Three
Direct proportion
When more of A means more of B: A/B = C/X, so X = (B × C) / A. If 3 apples cost $2, 10 apples cost (2 × 10) / 3 = $6.67.
Inverse proportion
When more of A means less of B, like workers and time to finish a job: A × B = C × X, so X = (A × B) / C.
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