Maths & numbers
Proportion calculator
Solve a / b = c / x for the missing fourth value.
A clear answer. Here’s how.
Cross multiplication gives x = b × c / a. The first numerator and denominator must be non-zero. Degenerate zero-denominator solutions are rejected.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- a (first numerator)
- 3
- b (first denominator)
- 4
- c (second numerator)
- 9
Example result
- x
- 12