Math
Fraction arithmetic
Add two fractions and simplify the result.
Calculators / Math / Solve a proportion
Solve a proportion calculator
Find the missing fourth value in two equal ratios.
On this page
Missing denominator d8
Calculator controls
How to calculate
Find the missing fourth value in two equal ratios.
Missing denominator d = b*c/a
Worked example
First numerator a: 3; First denominator b: 4; Second numerator c: 6.
Missing denominator d: 8 .
Assumptions and limits
Not in this arrangement. A zero numerator can leave the missing denominator undetermined; use a different algebraic form for that case.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
The missing value satisfies a/b = c/d. All denominators and the resulting d must be nonzero for a valid proportion.
When this tool is useful
Find the missing fourth value in two equal ratios.
Understanding your inputs
| Input | What to enter |
|---|---|
| First numerator a | Enter a number of at least -1000000000000 and no more than 1000000000000. |
| First denominator b | Enter a number of at least -1000000000000 and no more than 1000000000000. |
| Second numerator c | Enter a number of at least -1000000000000 and no more than 1000000000000. |
Frequently asked questions
Can I use zero for a or c?
Not in this arrangement. A zero numerator can leave the missing denominator undetermined; use a different algebraic form for that case.