variationVariation2004-12-14 15:28:282005-01-29 09:51:27TopicRelationships between two or more variables.% this is the default PlanetMath preamble. as your knowledge
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% define commands hereVariation and proportion are defined to be the relationship between two or more variables with regard to a constant of proportionality.
The traditional notation for direct proportionality is $x \propto y$ or, if using regular equality notation, $x = ky$.
Here, $k$ denotes the constant of proportionality.
Similarly, the traditional notation for inverse proportionality is $x \propto 1/y$ or, with regular equality, $x = k/y$.
For direct proportionality, to find the value of an unknown $x$ or $y$, you may use the formula:
$y_{1}/x_{1} = y_{2}/x_{2}$
Similarly, for inverse proportion it would be:
$x_{1}/y_{1} = y_{2}/x_{2}$