Rule of Three: Direct and Inverse Proportions

The rule of three is a procedure for calculating the value of a quantity from the proportional relationship between other known quantities.

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X = (B × C) / A

When to use this tool

Unit conversion, recipe adjustment, dosage calculation, proportions in chemical solutions, and linear relationships in physics.

How it works

In direct proportion, if A→B then C→X where X = (B×C)/A. In inverse proportion, X = (A×B)/C. A fundamental tool in science for quickly solving proportions.