Direct Proportion Rule of Three Calculator
Project the unknown term X in a direct proportion by cross-multiplying A, B, and C, with optional control over decimal precision.
Educational aid for proportional reasoning; verify against domain-specific standards before official use.
Examples
- 4 hours produce 28 components, 9 hours ⇒ 63.00 units of B
- 2.5 L cost $18.75, 4.2 L with precision 3 ⇒ 31.500 units of B
FAQ
How does this tool compute the missing value?
It applies the direct rule of three: multiply B by C and divide by A while preserving the proportional relationship.
What happens if I enter zero for A?
The calculator will return a reminder that A must be nonzero because dividing by zero makes the proportion undefined.
Can I change the number of decimals in the result?
Yes. Enter an integer between 0 and 6 in the optional decimal places field; leaving it blank defaults to two decimals.
Additional Information
- Results are presented in the same unit as input B with U.S. decimal formatting.
- Negative numbers are allowed; the sign of the result follows the sign pattern of the inputs.
- Optional decimal places accepts whole numbers from 0 to 6 and falls back to two decimals when left blank.