Solve proportional and inverse rule-of-three problems: if A corresponds to B, what does C correspond to?
How to use the Rule of Three
Enter the known pair: A corresponds to B.
Enter C, the value you want to scale.
Choose proportional or inverse and read the result.
Frequently asked questions
A method to find an unknown value from a known ratio. If A corresponds to B, then C corresponds to B times C divided by A (proportional).
When the quantities move in opposite directions: as one goes up, the other goes down. For example, more workers means less time, so the result is A times B divided by C.
Yes. All four values and the result can be decimals, so it works for prices, quantities, speeds and time.
A rule of three (Dreisatz) calculator for proportional and inverse relationships, a staple of everyday maths and school exercises.
Enter the known pair and the value to scale, pick the relationship type, and get the answer instantly.
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