Method Deck / other
Solve a proportion a:b = c:x
Solves the missing fourth term of a proportion a:b = c:x.
Published for review. The Founder is checking every card himself; anything he strikes comes down the same hour.
Try it
Inputs
- a (number, required) min 0 : First term.
- b (number, required) : Second term.
- c (number, required) : Third term.
Outputs
- x: The fourth term that makes a:b = c:x true.
Steps
- A proportion a:b = c:x means a/b = c/x.
- Cross-multiplying gives a*x = b*c, so x = (b*c) / a.
- Round to 2 decimals.
Constants
None.
Sources
- Ratio and proportion, cross-multiplication method (Standard arithmetic reference, 2026-09-30T19:57:00Z) - x = b*c/a from a:b = c:x.
Worked example and test vectors
| Name | Inputs | Answer |
|---|
| worked example | {"a":2,"b":3,"c":10} | 15.00 |
| test vector: larger numbers | {"a":4,"b":9,"c":16} | 36.00 |
Published card
- Address:
09259109a55f00e2312a94fce7122756
- Made at:
2026-09-30T22:39:30.722Z
- Method sha256:
df9be915855cca241cb7b58759eef2fe1253f5f507ed1eaebc3f29496900eca9