Similar Triangles is a task created for geometry students learning how to determine if triangles are similar based off of side lengths. Students are given two triangles and the lengths of every side and must construct an argument as to whether they are similar or not. Sentence starters and argumentation language are provided to encourage a claim and the use of evidence.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_Worksheet_Construct_SimilarTriangles

PDF version: 912Geometry_SRT_SimilarTriangles_Worksheet_Construct_SimilarTriangles


Not in my Backyard is a task developed for geometry students learning about similar triangles. The task asks students to critique a student’s argument that two triangles are similar. Students must construct an argument and the task uses argumentation language including claim and evidence. The task suggests having students use the argument writing frame first, then constructing the argument. The task addresses a common misconception about similar triangles, that if you add the same number to each side and get the other triangle, then triangles are similar. Students must know the difference between proportions and differences.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_Worksheet_ConstructCritique_NotinmyBackyard

PDF version: 912Geometry_SRT_SimilarTriangles_Worksheet_ConstructCritique_NotinmyBackyard


Casting Shadows is a task on similar triangles for geometry students. In the problem, one fourth grader knows his height and shadow length and wants to use similar triangles to determine another fourth grader’s height, when only knowing the shadow length. Students are to critique the proof given on the height of the other fourth grader and construct their own response, using a template, claim, evidence and warrants.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_Worksheet_ConstructCritique_CastingShadows

PDF version: 912Geometry_SRT_SimilarTriangles_Worksheet_ConstructCritique_CastingShadows