Blow up a solid by a scale factor. A section of a larger playlist on basic geometry introduces the ratios of the surface areas and volumes of similar solids. Using the ratios, the video works several examples involving similar figures.

Find the square of the scale factor. A component of a large playlist on geometry discusses the ratios of the perimeters and areas of two similar polygons. The resource shows examples in finding the ratios that lead to a pattern.

Develop an understanding of the scale of similarity. Starting with the concept of congruency, the resource introduces the idea of similarity between two figures. As part of a larger playlist on geometry, it defines similarity and uses...

Investigate and compare scale factors of perimeter and area. Young scholars use an applet to manipulate the sides of similar rectangles. They then make perimeter and area calculations and compare the ratios to finish the second in a...

The definition of similar to a mathematician is a little different than the average person. The first in a sequence of four lessons asks learners to investigates the criteria for similar figures. They compare side lengths between similar...

Let your scholars foreshadow unknown heights. The class uses proportions to solve height problems. Using the ratio of their shadows to their heights, pupils calculate the heights of objects by measuring the shadows. The lesson is the...

Build similar figures from congruent ones. The lesson introduces the concept of rep-tiles. Pupils show that given figures are rep-tiles and discuss the difference between composing and decomposing the tiling patterns.

Zoom in to reveal more of the same. The resource introduces the concept of self similarity. Using a simple example, the video—part of a larger playlist covering geometry concepts—illustrates the meaning of a self similarity figure.

Multiply coordinates to either shrink or enlarge a figure. An informative segment of a geometry playlist introduces dilation on the coordinate plane. The dilations in the resource use the origin as the center of dilation, which makes...

Forget flying, let's go build a kite! Groups build a paper tetrahedron from two 3-D folded figures. They then combine multiple tetrahedrons teams to make a larger tetrahedral kite and compare the surface areas and volumes.

Just a sip will make things smaller. Using Alice’s Adventures in Wonderland as a hook, the lesson introduces the idea of similarity. Pupils use it to find the distances on a map by applying the scale factor and creating similar triangles.

How high and how far does it go? Young scholars learn to count slope by drawing congruent triangles. The activity highlights the difference between positive and negative slope.

Are two angles enough? Given two triangles, the class determines through the definition of similarity and transformations whether the two triangles are similar. Provided with pairs of triangles and measurements, small groups find out...

Are all the measurements scalable? Pupils work in groups or alone to determine whether figures are similar and find any missing side lengths. Then, they calculate the perimeters and areas of the figures. Finally, using the measurements,...

How do you measure a distance where the measurement tool will not reach? Pupils use the concept of similar triangles to perform indirect measurements. The lesson asks teachers to demonstrate the method and lead the class through a set of...

Scale up the dilation factor. Using a dynamic geometry software program, classmates discover the relationship between a pre-image and its image after performing a dilation. Individuals create their own dilations and fellow class members...

Just how similar are dilations to isometries? The lesson builds upon pupils' knowledge of transformations and introduces the concept of dilations to obtain similar figures. Learners find out how to dilate a figure without the coordinate...

What does every circle have in common? Learners explore this question as they prove all circles are similar. A series of activities leads them to this conclusion by identifying transformations.

Dilated pupils, the way to prove circles are similar. Using the knowledge of dilations of polygons, class members learn how to dilate a circle to show that it is similar to any other circle. The teacher guides the class through a proof...

Show similarity with a similar approach to congruence. The assessment provides learners with two figures on a coordinate plane. Pupils use the coordinates of the figures and similarity transformations to describe how to show the two...

Develop a proof of the general case. Pupils develop a proof using transformations to prove the general case that any two circles are similar. The assessment provides minimum information about the two circles.

Use scale factors to find areas of circles. Pupils delve deeper into the informal argument for the formula of the area of a circle. The scholars show the relationships of areas of similar polygons also holds true for circles.

What happens to a dilation when the scale factor is less than one? Learners show and then tell this in a short worksheet. They create a dilation from an off-line point using a scale factor of 0.5. The class then explains how the images...

Assessing progress is easy using a quick quiz focused on dilations with the center on the line! Geometry geniuses graph the images of points resulting from a dilation with a center point. Then, they must describe the relationship between...