Lesson plan

You Be the Judge!

Give students an opportunity to practice subtraction and analyze their peers' work with this fun lesson. Young mathematicians will have a great time playing a judging game and completing quirky worksheets.
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Students will be able to use different subtraction methods.

(5 minutes)
  • Ask the class to have a discussion on what they know about subtraction.
  • Ask students to name some mental strategies they use in order to solve subtraction problems.
  • Create a list of strategies on the board, e.g. decomposing, number bonds, tape diagram, and regrouping.
  • Tell students that today, they will play a subtraction game called You Be the Judge. The game will give them a chance to anonymously judge their classmates' thinking and solutions.
(5 minutes)
  • Explain that all students will solve a given subtraction problem, but only three contestants will be judged.
  • Tell the class that each student will receive materials to help them solve the given equation.
  • Write "74 - 31" on the board.
  • Explain that each student will solve the subtraction problem using a strategy that works best for them on their whiteboards. Students not being judged will be able to compare their work to that of their classmates.
  • Inform students that in the first round, the teacher is the judge. The judge stands in the back of the room, with their back towards the class. The judge cannot view student work, and will only be called to the front when all three contestants have finished and displayed their work.
  • Tell students that no names can appear on the work. This helps the judge assess their work fairly.
  • Tell students the judge will select the work they admire the most and will provide an explanation on why it was selected. The student whose work was chosen will become the new judge, and three new contestants will be chosen while the judge is looking away.
(10 minutes)
  • Pass out whiteboards, markers, and erasers to each student.
  • Explain that all students will be responsible for solving a subtraction problem given by the teacher, but only three will be judged.
  • Remind students to solve the subtraction problem with a strategy that works best for them.
  • Write "58 – 33" on the board. Tell students that they will play a practice round, and you will be the first judge. For this game only, ask for three student volunteers. (Normally, the judge would not see who the three contestants are.)
  • When students are ready, stand at the back of the room, facing away from the class. After the three contestants have placed their whiteboards at the front of the class, students will let you know they are ready by saying aloud, “You be the judge!”
  • Examine each board, make a judgment, and provide an explanation on why that board was chosen. For example, it might have the correct solution, be easy to understand, and contain detailed information.)
  • The contestant whose board was chosen becomes the new judge.
  • Write a new subtraction problem, and have students select three new contestants while you look away.
(20 minutes)
  • Continue playing several rounds of the game.
  • Monitor students' work as the game is being played.
  • Have students complete either the Practice Subtraction: Corn worksheet or Color in the Circles worksheet independently.
  • Enrichment: Advanced students can work with a partner or small group to create their own subtraction equations, and have their classmates explain how they solved it. They can also work on the Dog Walking: Practice Subtraction worksheet as a challenge assignment.
  • Support: Provide small group instruction for struggling students by modeling various strategies. Complete the Practice Subtraction: Corn worksheet with them as a group.
(10 minutes)
  • Make visual observations as students work on their whiteboards during the game and work independently on their worksheets.
  • Assess them based on how well they understand different subtraction methods.
(10 minutes)
  • Ask students to share on their whiteboards what they enjoyed from today’s game.
  • Have students share their thoughts with the class.

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