In mathematics, we can say two variables which are directly propertional, then they are said to be in direct variation. For example, x and y are two variables, y is directly proportional
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The constant of proportionality involved in variation can be difficult for students at first, as it is written like a variable (usually k) but plays a different role in the equations
http://www.ehow.com/info_8719848_variationalgebra...

Variation of the set of measurements is the spread of the data.
http://wiki.answers.com/Q/What_is_variation

My favorites are. guava lemonade. watermelonade. I also like the Blue Bottle lemonade, which they make with yuzu.
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