Digital Skills: Developing Online Assessment Skills in Everyday Classroom Activities Western Reserve Public Media

Cut and Paste Proofs for Triangle Congruence

I can:
  • I can complete formal proofs to show triangles congruent.
Tech Skills:
  • Keyboarding

  • Drag and drop items

  • Next Generation testing skills

  • Access to Google Docs

Materials and Resources:

Cut and paste handouts

Proof Matching: In class activity

Drag and Drop Worksheet

List of triangle proofs

Computer for online Worksheet


Activity is best used as a formative assessment after introducing triangle congruence proofs

Grade Level:
  • 10th Grade
Subject Area:
  • Geometry


Bell Ringer

Explain how a person could prove .  Make sure to include an appropriate theorem with your explanation.


Activity 1

  1. The idea behind the lesson is two-fold. To complete the drag and drops proofs as seen on the EOC and check for student understanding of triangle congruence.

  2. Pass out the worksheet with two proofs listed and the statements and Reasons mixed up. Proof Matching: In class activity

  3. Have the students work in pairs to rearrange the statements and reasons to complete the proofs for the triangles.

  4. Debrief with the students about their strategies to complete the problems.



Activity 2

  1. On an interactive board or projector pull up the Drag and Drop Worksheet.

  2. Complete the first proof with the class to demonstrate how to manipulate the text boxes.

  3. Then have the students use whatever device they have to go to the link.

  4. I share the link through our Google Classroom. This way each student has his/her own copy and then turn it in as an assignment.

  5. Have the students work in class on the document. 

  6. Monitor their progress on the worksheet and topic.

  7. If using Google classroom you can pull up the students’ work in real time. 



Practice Activity

Teacher needs to assign homework to differentiated groups. Students need to be assigned clusters of proofs based on difficulty levels. This is up to the teacher to design and distribute.


G.CO.10 Prove and apply theorems about triangles. Theorems include but are not restricted to the following: measures of interior angles of a triangle sum to 180°; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.

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