This similarity warmup has geometry students focus on the definition of similar triangles and has students engage in one practice problem. Students are asked to fill in the blanks providing definitions for similar triangles, focusing on congruent angles and proportional side lengths. Students must construct an argument telling why two triangles are or are not similar.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_Warmup_Construct_SimilarityWarmup

PDF version: 912Geometry_SRT_SimilarTriangles_Warmup_Construct_SimilarityWarmup


This exit slip is for geometry students learning similarity. Two similar triangles are given and students must find the missing side lengths and scale factor. The final question uses argumentation language and asks students to construct an argument justifying the process of how one the side lengths was found.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_ExitSlip_Construct_SimilarityExitSlip

PDF version: 912Geometry_SRT_SimilarTriangles_ExitSlip_Construct_SimilarityExitSlip


Similarity and Dilations Warmup is geared towards geometry students. The task provides two triangles on a coordinate plane and asks students to determine if the triangles are similar and construct an argument that supports the answer. The task does not provide measurements of the sides of the triangle and requires students to be able to read the coordinate plane as well as identify similar triangles.

Microsoft Word version: 912Geometry_SRT_SimilarTriangles_Warmup_Construct_SimilarityandDilationsWarmup

PDF version: 912Geometry_SRT_SimilarTriangles_Warmup_Construct_SimilarityandDilationsWarmup


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