Catch the Mistake

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SWBAT find mistakes and correct the mathematical thinking of others.

Big Idea

Mathematical Practice 3 takes center stage as students critique the reasoning of others for problematic questions.


15 minutes

Catch the Mistake is a powerful exercise. I choose mistakes that I know are frequent and wide-reaching – students at all levels will make these common errors. Because of this, students must think deeply about the solution strategies that they are presented with and must think of why they are incorrect. Sometimes they must confront their own errant thinking because they will agree with everything that the student is doing in the solution strategy. I think this is a nice way to prepare for our midterm exam in a different way than just doing problems. It gives students practice for a test situation where they get an answer and it is not one of the choices.

I give students about 15 minutes to work on the worksheet with their table groups. This is an exercise where I will offer little to no help – I really want students to find the mistake themselves. However, I still go around and listen to try to notice general trends throughout the room.


15 minutes

After students have time to get through each of the three problems, I will choose a student to share their answer to each one. Sometimes I will choose students who focused on the incorrect mistake, to get a more rich discussion. For example, for #2 a student may disagree with the way that the a value was found, instead of noticing that the root -3 should have been repeated three times.

I discuss more about what I am looking for when students share in the video below.

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Midterm Review Packet

20 minutes

For the remaining portion of class, I will have students continue to work on the midterm review packet that they received yesterday. I will go around and answer individual questions or address the whole class if I feel it is needed.