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2016a.00550 Johnson, Heather Lynn Predicting amounts of change in quantities. Math. Teach. Middle Sch. 19, No. 5, 260-264 (2013). 2013 National Council of Teachers of Mathematics (NCTM), Reston, VA EN F93 G33 I23 mathematics of change covariation perspective elementary algebra rectangle-area problem rectangle-resizing problem lower secondary quantitative reasoning relationships between quantities change in quantities covariational reasoning rectangles area height length noninteger amounts of change diagrams linear functions propaedeutics From the text: Analyzing relationships between quantities can support middle-grades students' reasoning about algebra and function. When students focus on relationships between quantities in a function, they are reasoning covariationally. A student taking a covariation perspective might think about a function as a special relationship between quantities in which change in one quantity depends on change in another quantity. Students often have to wait until calculus to study the mathematics of change. A focus on relationships between quantities is one way to introduce middle-grades students to the mathematics of change. My intent with this article is to illustrate how predicting amounts of change in quantities can promote students' covariation perspectives. I provide examples of their work to illustrate different ways in which students have viewed relationships between quantities to make sense of a linear situation.