Proportion Calculator
Solve a missing value in a proportion or check whether two ratios are proportional using cross multiplication.
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Formula: A ÷ B = C ÷ D. Leave exactly one field blank to solve the missing value, or fill all four fields to check the proportion.
Results
Answer
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Proportion status
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First ratio
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Second ratio
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Completed proportion
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Cross products
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Decimal comparison
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Calculation details
Use this Proportion Calculator to solve a missing value in a proportion or check whether two ratios are equal.
Calculation Method
A proportion has the form:
A ÷ B = C ÷ D
For a valid proportion, the cross products are equal:
A × D = B × C
Cross multiplication can therefore be used to solve whichever value is missing.
Example
Solve:
6/9 = x/15
Cross multiply:
6 × 15 = 9x
90 = 9x
x = 10
Therefore, 6/9 = 10/15.
Important Note
The denominator values cannot be zero because division by zero is undefined.