LEARN NC

K–12 teaching and learning · from the UNC School of Education

Proof puzzles

Students will work in small groups to put geometric proofs that have been cut apart in the correct order. They will organize statements with the correct reason. A recorder in the group will write the finished product for the group to turn in to the teacher.

A lesson plan for grades 9–12 Mathematics

By ann mewborn

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Learning outcomes

Students will practice writing formal two column geometric proofs involving congruent triangles and congruent corresponding parts.

Teacher planning

Time required for lesson

55 minutes

Materials/resources

This activity will require about five or six sets of proofs that have been written, cut apart, and put in separate envelopes.

Pre-activities

Students will need to be familiar with SAS, ASA, SSS, and c.p.c.t.c. They will also need to be familiar with writing formal two column proofs.

Activities

  1. The teacher will need to type several proofs, cut them apart, and put the pieces in separate envelopes. (I suggest running each proof on a different color sheet of paper before cutting them apart.)
  2. Students will divide into groups of four. Each group will get an envelope. The students will put the proof puzzles together in the correct order. Each person can copy the completed proof and/or a recorder can copy for the group so each group will turn in only one copy of each proof.
  3. When a group finishes one proof, they put the puzzle back in the envelope, turn it in, and get another envelope and repeat the process. Each group should be able to complete three or four proofs in a class period.

Assessment

Each group will turn in a copy of their completed proofs. The teacher will give each group a grade based on their work. Each member of the group will receive the group grade.

Supplemental information

Comments

This activity works really well with students the day before a holiday break because it is a different approach to writing formal two column proofs.

North Carolina Curriculum Alignment

Mathematics (2004)

Grade 9–12 — Geometry

  • Goal 2: Geometry and Measurement - The learner will use geometric and algebraic properties of figures to solve problems and write proofs.
    • Objective 2.02: Apply properties, definitions, and theorems of angles and lines to solve problems and write proofs.