## Common Core State Standards for Mathematics

Grade(s) 4 resources related to the following standard:
Geometry
Draw and identify lines and angles, and classify shapes by properties of their lines and angles.
2. Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.

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This article gives teachers background information on right angles. It provides geometric and practical examples, a paper folding construction method, and some history of the usage of the term 'right.'
Reference Materials, Article
Resource is part of a PD collection
In this activity, students investigate the possible sizes and orientations of squares in a 4 by 4 grid. They are to place as many counters as they can on the grid and avoid making the four corners of any square. Solutions require working systematically. Ideas for implementation, extension and support are included along with printable worksheets of grids (.doc)
Activity
This interactive Java applet simulates the traditional Chinese tangrams puzzle that allows users to develop spatial reasoning skills. Users may explore freely, solve any of the 14 puzzles included, or work through four other sets of challenges. Users can rotate and flip pieces and change their colors. Some background, instructional uses and instructions are provided.
Activity, Interactive Media
Grade Level: 2, 3, 4, 5, 6+
This interactive Java applet provides practice in sorting triangles by type using a visual representation. Students drag scalene, isosceles, equilateral, right, and non-right triangles into Venn diagrams. Feedback on the students' choices is provided. An animated tutorial can be viewed first and at later times.
Activity, Interactive Media
This webcast presents the proceedings of an educator workshop given by Dr. Akihiko Takahashi, Professor of Mathematics Education at DePaul University. The series of videos summarizes research of the Van Hiele levels 0, 1, and 2, and features scenes from the educator discussions and from classrooms of grade 4 and 5 students working the lessons. The overriding principle of the forum is the active noticings of both groups and the opportunity to discuss them. Videos are downloadable in both Quick Time and Windows Media formats. A viewer guide (pdf) is available.
Instructional Strategy, Instructor Guide/Manual, Lesson Plans, Unit of Instruction, Video