Proportion Calculator
Solve the fourth value that makes two ratios equal.
Result
Missing value X: 16
The result makes A ÷ B equal to C ÷ X.
- A divided by B
- 0.75
- C divided by X
- 0.75
- Equal cross product
- 48
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Results follow the mathematical operation and values shown. Check that you selected the intended operation, convention and dataset type before relying on the result. Read the full disclaimer
How to use the Proportion Calculator
- Enter A, B and C for the equation A divided by B equals C divided by X.
- Read the solved fourth term X.
- Compare both displayed ratios to verify that the proportion is equal.
Solve one equivalent ratio
The calculator uses the fixed arrangement A/B = C/X. Cross multiplication
produces A×X = B×C, so:
X = B × C ÷ ABoth resulting ratios and the shared cross product are displayed as checks. Cross multiplication applies because the expression is exactly an equality of two ratios.
With your numbers
- Set 3/4 equal to 12/X.
- Cross multiply and divide: X = B × C ÷ A = 16.
Quick reference
The result makes A ÷ B equal to C ÷ X.
| Example | Missing value X |
|---|---|
| 3/4 equals 12/x | 16 |
| 2/5 equals 8/x | 20 |
| 7/9 equals 21/x | 27 |
| 1.5/2 equals 6/x | 8 |
| 10/4 equals 25/x | 10 |
| 5/5 equals 12/x | 12 |
Common questions about the Proportion Calculator
- What is a proportion?
- It is an equation stating that two ratios are equal.
- How is X solved?
- Cross multiplication gives A times X equals B times C, so X equals B times C divided by A.
- Can A or B be zero?
- Not in this arrangement. A is the divisor used to solve X and B is the denominator of the first ratio.
- Can the values be decimals?
- Yes. The relationship uses division and does not require whole-number terms.