Background review and examples are complete.
Teacher will open the discussion by challenging students to give real-world examples involving ratios or proportions. (Examples: basketball statistics, recipes, etc.)
Opening Activity - Reading Connection
Teacher will have students skim Alice's Adventure in Wonderland to find other references to ratios. The following link should be used for this activity:
Note: Click Chapters 1, 2, or 5 for this activity. Depending on the makeup of the groups, each group can be assigned a different chapter. The same chapter can be assigned to the groups to encourage friendly competition.
The information in the story will be used to make up several problems about ratios that Alice might use to help her understand her surroundings. Students will share their problems.
The lesson will continue with the introduction and definition of similar figures.
Definition of Similar Polygons
Two polygons are similar if and only if their corresponding angles are congruent and the measures of their corresponding sides are proportional.
Teacher will present several pairs of similar polygons on the document camera along with several pairs of polygons that are not similar. Students will be asked to make observations and defend their responses with mathematical processes. Teacher will point out that a document camera shows an image on a screen that is similar to the image on the document. Students will be asked to think of other devises that form similar images. (enlarger, photocopier, etc)
The following web link will reinforce this demonstration:
Scale Factor Activity:
Using maps provided by the teacher, students will practice reading scales. Next, a base location and a destination will be chosen. Students will then compute the distance between the two points as well as the time it takes to travel between the two points.
Error: Teacher will remind students to avoid giving one ratio in the wrong order. Prescription: Students will be encouraged to write words to name the quantities on both sides.
The following web link will be used to reinforce this demonstration:
Since this lesson explores similarity rather than verify similarity, the following hands-on activity will be used to check students' understanding.
Teacher will have each student use a straight edge to draw a triangle. Students will then be asked to measure the sides of the triangle and draw a similar triangle with a scale factor of 1/2. Students will be asked to explain how they know the triangles are similar.