Direct and inverse proportion
Constant-ratio and constant-product relationships.
Key knowledge
For positive x and y, direct proportion means y=kx with fixed k>0, so y/x stays constant. Inverse proportion means y=k/x, so xy stays constant. The constants in the two relationships are separately defined.
Values and equations
direct: y=k_d x; inverse: y=k_i/x
- x, y
- Positive variables declared quantity units
- k_d
- Fixed positive direct-proportion constant y-unit/x-unit
- k_i
- Fixed positive inverse-proportion constant x-unit·y-unit
Conditions and scope
- The same constant must apply throughout the stated domain, with other influences held fixed.
- State the units: a direct-proportion constant has y-units per x-unit, while an inverse-proportion constant has their product.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Constant-ratio and constant-product relationships.
2026-10-10 · Independent Physics and Measurement reference editor (AI editorial bounded review). Exact bounded introductory reference claims and this practical concept inventory are approved after closure. Existing university/research proof and source scopes remain separate; no universal knowledge-completeness or experimental-validation assertion.
Foundational review
2026-10-10 · Independent AI editorial inspection of this new compact reference entry, its equations, applicability, sources and knowledge connections.
Sources from other places
Agreement within this scope
Positive direct proportion has constant ratio; inverse proportion has constant product.
The source ratio x/y uses the reciprocal of the constant in repository y=kx.
National Council of Educational Research and Training
- Mathematics Exemplar · Direct and inverse proportions IndiaEnglish
Unit 10: Main concepts and results, PDF pp.1–2
- Mathematics Exemplar · Direct and inverse proportions
Entry details
Permanent link to this entry ↗- Record identity
- foundation-math-direct-inverse-proportion
- Revision
- foundations-audit.1
- Structured reference record
- Foundational core completion