From site:
InterMath is a professional development effort designed to support [middle school] teachers in becoming better mathematics educators. It focuses on building teachers’ mathematical content knowledge through mathematical investigations that are supported by technology. InterMath includes a workshop component and materials to support instructors…
The InterMath materials are organized into four key mathematical strands (Number Sense, Algebra, Geometry, and Data Analysis). Under these 4 strands, there are 13 units: Fraction and Decimals, Integers, Ratios Proportions & Percents, Quadrilaterals, Triangles, Polygons, Probability, Statistics, Solids, Circles, Graphs, Patterns, Functions & Equations. The InterMath problem set is comprised of open-ended investigations which are problems that have at least one of the following attributes: multiple solutions, multiple approaches to solving them, and multiple entry points.