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Solve a proportion for an unknown

Solve a/b = c/x for the missing fourth term.

Also known as: solve a proportion for an unknown calculator, proportion calculator, solve 3/5 = x/20, solve a proportion for an unknown, proportions math, proportions solve a proportion for an unknown

Inputs

Missing term

Results update when you click Solve.

Fourth term

8.0000

3.0000/4.0000 = 6.0000/8.0000

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What this result means

Solve a/b = c/x for the missing fourth term. Cross-multiply: a·d = b·c, then isolate the unknown.

Assumptions

  • Rule dependency: Universal formula.

How is it calculated?

Cross-multiply: a·d = b·c, then isolate the unknown.

Example

3/4 = 6/x → x = 8.

Frequently asked questions

Units?+

Keep units consistent across numerators and denominators.