Curated OER
Analyzing Congruence Proofs
Looking at numerous examples of triangles, each with different properties, geometers develop their understanding of congruency. They use the notation of a counter-example to disprove certain conjectures and prove geometric theorems and...
Flipped Math
Unit 6 Review: Similar Figures
After a short review of the material from the Similar Figures Unit, pupils work through 18 problems to further practice the skills from the unit. Scholars apply those skills in the application problems at the end of the review.
Flipped Math
Side Splitter Theorem
Apply perspective to similarity. Individuals learn about the Side Splitter Theorem by looking at perspective drawings. Pupils use the theorem and its corollary to find missing lengths in figures. Next, they practice using the theorem and...
Flipped Math
Prove Triangles Similar
Show more than one way to prove similarity. Scholars learn three different methods to show two triangles are similar, Angle-Angle, Side-Side-Side, and Side-Angle-Side. Pupils practice applying these methods to determine whether two given...
Radford University
REALLY Tall!
Conduct indirect measurements three ways. Working in groups, pupils come up with different ways to measure three tall objects indirectly. The teacher provides measurement information requested by the teams, and learners then calculate...
Radford University
Build-a-Toy
Don't toy with using a fun lesson. Scholars design new toys and then create scale drawings. They determine the volume and surface area of the toys, and then research prices of raw materials to estimate the manufacturing costs.
Radford University
How Tall is the Tree?
Pairs or small groups work together to determine the height of a tree using similar triangles. Learners make a judgement which direction to let a tree fall to avoid hitting any structures. They then write letters to the principal...
Radford University
Triangular Irrigation
Try to keep the pipe short. Learners investigate where to place a water pump to use the least amount of pipe. Scholars use their knowledge of reflections and congruent triangles to find the best location for the water pump. Finally, they...
Radford University
Next Top Model
Create a world of similar models. The geometry and measurement unit uses real-world scenarios to create models of familiar buildings and rooms. Scholars work with blueprints and scale models to compare areas and volumes between the...
Radford University
Catch Me If You Can!
Crime doesn't pay, but everyone can learn from it. Learners consider different situations involving mischief at a school, such as stink bombs and rockets, and analyze them using mathematics. They must apply trigonometry, quadratic...
Concord Consortium
Short Pappus
It's all Greek to me. Scholars work a task that Greeks first formulated for an ancient math challenge. Provided with an angle and a point inside the angle, scholars develop conjectures about what is true about the shortest line segment...
Concord Consortium
Proportional Representation
Sometimes the solution is all a matter of perspective. The short assessment task presents a problem to pupils that requires them to make sense of a diagram. Once learners see two similar triangles, the rest of the solution is solving a...
Mathematics Vision Project
Module 4: Similarity and Right Triangle Trigonometry
Right you are to use a great resource. Starting with a lesson on dilations, scholars learn about similarity transformations and similar triangles. They use the knowledge to develop an understanding of right triangle trigonometry in later...
Concord Consortium
Mirror, Mirror I
How do you see yourself? Young mathematicians consider whether it's possible to view their whole bodies in a mirror with a length that is half their height. They write a letter to a friend explaining their positions mathematically.
National Council of Teachers of Mathematics
Bank Shot
Bank on geometry to line up the shot. The resource asks the class to determine the location to bank a cue ball in a game of billiards. Using their knowledge, class members determine where to hit the bumper to make a shot and discuss...
Yummy Math
Parametric Equations and a Heart
Trigonometry, art, and Valentine's Day come together in a creative activity about parametric equations. Learners calculate several equations before graphing them either by hand, on a graphic calculator, or Excel spreadsheet to curve...
Education Development Center
Similar Triangles
Model geometric concepts through a hands-on approach. Learners apply similar triangle relationships to solve for an unknown side length. Before they find the solution, they describe the transformation to help identify corresponding sides.
Virginia Department of Education
Similar Triangles
Pupils work in pairs to investigate what it takes to prove that two triangles are similar. They work through various shortcuts to find which are enough to show a similarity relationship between the triangles. Small groups work with the...
Mathematics Assessment Project
Modeling Motion: Rolling Cups
Connect the size of a rolling cup to the size of circle it makes. Pupils view videos of cups of different sizes rolling in a circle. Using the videos and additional data, they attempt to determine a relationship between cup measurements...
Inside Mathematics
Rhombuses
Just what does it take to show two rhombuses are similar? The assessment task asks pupils to develop an argument to show that given quadrilaterals are rhombuses. Class members also use their knowledge of similar triangles to show two...
Inside Mathematics
Hopewell Geometry
The Hopewell people of the central Ohio Valley used right triangles in the construction of earthworks. Pupils use the Pythagorean Theorem to determine missing dimensions of right triangles used by the Hopewell people. The assessment task...
Balanced Assessment
Modern Building
Turn your pupils into emerging architects with a resource that asks learners to analyze a scale drawing of a building. They use the scale drawing to interpret the size of the actual building before recreating the drawing using a...
Mathematics Assessment Project
Deducting Relationships: Floodlight Shadows
Try to figure out what happens with shadows as a person moves between two light sources. A formative assessment lesson plan has individuals work on an assessment task based on similar triangles, then groups them based on their assessment...
Mathematics Assessment Project
Evaluating Statements About Length and Area
Class members complete an assessment task by identifying whether statements about triangles and quadrilaterals are always true, sometimes true, or never true. They then participate in a sorting activity with the same objective.