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Proportion Calculator
Solve proportions of the form A : B = C : X by finding the missing term.
About the Proportion Calculator
Solve proportions of the form A : B = C : X by finding the missing term.
How to use the Proportion Calculator
- Enter A, B and C.
- Use Add Proportion Field to solve several at once, and read the value of X.
Formula and method
A ÷ B = C ÷ X, so X = (B × C) ÷ A.
Worked example
If 3 : 4 = 9 : X, then X = 4 × 9 ÷ 3 = 12.
Tips
- Use proportions for scaling recipes, map distances and currency.
- The four terms must be in matching order.
Frequently asked questions
What is direct proportion?
Two quantities that increase together at a constant ratio.