Curated OER
Understanding Proportions and Scale Drawings
Proportions are ratios found using multiplication or division. Middle schoolers solve measurement problems, find a figure's missing dimension, and find the distance between two points. Resource features four lesson plans with detailed...
EngageNY
The Angle-Angle (AA) Criterion for Two Triangles to Be Similar
What do you need to prove triangles are similar? Learners answer this question through a construction exploration. Once they establish the criteria, they use the congruence and proportionality properties of similar objects to find...
Curated OER
Effects of Changing Dimensions Proportionally
In this geometry instructional activity, learners describe the effect of a proportional change on the perimeter or circumference and area of the given circles or quadrilaterals. The one page instructional activity contains ten...
West Contra Costa Unified School District
Investigating Similar Triangles
Let your use of the resource be in proportion to its usefulness. Pupils investigate similar triangles by measuring side lengths and considering given angle measures. The results of the investigation help develop generalizations about...
EngageNY
More About Similar Triangles
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...
EngageNY
Special Relationships Within Right Triangles—Dividing into Two Similar Sub-Triangles
Why are right triangles so special? Pupils begin their study of right triangles by examining similar right triangles. Verifying through proofs, scholars recognize the three similar right triangles formed by drawing the altitude. Once...
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...
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...
Willow Tree
Ratios and Proportions with Congruent and Similar Polygons
Investigate how similar and congruent figures compare. Learners understand congruent figures have congruent sides and angles, but similar figures only have congruent angles — their sides are proportional. After learning the...
Curated OER
Similar Triangles
Tenth graders practice solving proportions from similar triangles. They watch a PowerPoint presentation and complete a worksheet each of two days of this lesson. Links for worksheets and PowerPoint presentations are included with this...
Curated OER
Unit 5: Worksheet 3 - Similar Triangles
In this similar triangles worksheet, students use proportions to solve for the missing sides of similar triangles. This two-page worksheet contains 16 multi-step problems.
University of Utah
Explore Proportional and Linear Relationships
Progress from proportional relationships to linear functions. Pupils first review concepts of proportionality covered in earlier grades. They then extend these concepts to linear functions, such as determining the slope of a line using...
EngageNY
The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar
Playing with mathematics can invoke curiosity and excitement. As pupils construct triangles with given criteria, they determine the necessary requirements to support similarity. After determining the criteria, they practice verifying...
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.
EngageNY
Similarity and the Angle Bisector Theorem
Identifying and verifying reproducible patterns in mathematics is an essential skill. Mathematicians identify the relationship of sides when an angle is bisected in a triangle. Once the pupils determine the relationship, they prove it to...
EngageNY
Modeling Using Similarity
How do you find the lengths of items that cannot be directly measured? The 13th installment in a series of 16 has pupils use the similarity content learned in an earlier resource to solve real-world problems. Class members determine...
EngageNY
Prove the Pythagorean Theorem Using Similarity
Amaze your classes with the ability to find side lengths of triangles immediately — they'll all want to know your trick! Learners use the Pythagorean Theorem and special right triangle relationships to find missing side lengths.
Curated OER
Similar Triangles and Proportions
Pupils investigate similar triangles and proportions as they make conjectures about the length of sides of similar triangles. For this lesson, have your class construct similar triangles using Cabri Jr so that they share a common vertex.
Curated OER
Indirect Measurement with Similar Triangles
Young scholars use similar triangles to find missing heights. In this using similar triangles to find missing heights lesson, students use proportions to find the heights of missing side lengths. Young scholars find the height of trees...
Curated OER
Chapter 8 Extra Problems Worksheet: Similar Triangles
In this similar triangles worksheet, students solve 6 similar triangles. Students use proportions to solve similar triangles and similar rectangles.
Curated OER
A Geometry Worksheet - Similar Triangles
In this similar triangles activity, students find the scale factor of 6 sets of similar triangles. Students find the scale factor of two similar triangles given a sketch with measurements. Students use proportions to find a missing side...
Curated OER
Kuta Software - Infinite Geometry: Similar Triangles
In this similar triangles worksheet, students solve 20 short answer problems. Students determine if two given triangles are similar. Students determine the type of similarity given two triangles. Students are given a sketch of the...
Curated OER
Effects of Changing Dimensions Proportionally
In this geometry worksheet, 10th graders examine the effect of changing the dimensions of a figure proportionally on the perimeter, circumference, and area. The one page worksheet contains six problems. Answers are included.
Curated OER
Math Hw #15: Proportions
In this proportions worksheet, students solve 8 word problems. Students determine the cost of an item given a unit cost. Students find a missing side length of a triangle using proportions of similar triangles.