I really like congruent triangles. It is one of my favorite units in Geometry. I have lots of activities for congruent triangles and the kids are finally starting to get used to proofs.
Throughout the unit, I constantly remind my students that they need three pieces of information to show that the triangles are congruent. To reinforce that idea, a colleague made this activity a couple of years ago, and I really like using it.
First print all of the little matching cards. You can download the file here. All of the pieces look like this.
When, I copied the matching cards, I used a different color for each “problem”. That way, I didn’t have to number the bags or worry about pieces getting lost. It took some organizing though. Each problem has four pieces. So, I made sure that one of the SSS problems was light blue for all of the pieces. When matched, the pieces look like this:
All together, I have three sets of each problem. That way, I don’t have to have a bag of each one for every student. They just return the bags as needed.
When the student takes a bag, they sort through the pieces. They decide which piece of information is not needed to prove the triangles are congruent by the given theorem or postulate. Then, they record the information on their recording sheet. (Go ahead and click the blue download button. It says the file type isn't supported, but if you go ahead and download it, everything works fine.)
This works really well for my students. It’s like they are working on little mini-proofs. If you try this, I hope it works well for you!