Nacho Problem

What’s a problem that’s not yours? Nacho Problem!

It’s that time of year, Test Prep time. Which makes me think about using EduProtocols for Test Prep. One great one that really promotes deeper thinking and understanding is Nacho Problem. This was created by Ligia Ayala-Rodriguez. It’s a fun way to do error analysis with your students. I have done this with students as young as 7.

One of the advantages is that you begin by telling the students the answer is wrong. This seemingly takes the pressure off. I like to have the students talk it out the first few times. I guide them along the way to help set the expectations. Just like in an ‘Analyze the Error’ on the test, students are expected to express their thoughts in writing. This can present an additional challenge if they haven’t exercised this skill. I’m not saying we should do this solely to prepare for the state test; the benefits of students being able to do this go far beyond that idea.

How to Get Started

As a class, they are presented with a Nacho Problem. We read and analyzed the problem together; starting with “What do you notice?” and “What do you wonder?” I explicitly tell them the answer is wrong and that we must find where I went wrong. I have found that looking at the question and working out the problem allows us to focus on the process (that the problem is asking us to solve) rather than the arduous task of finding a mistake. Once we work it out together, and later independently, students can then go back and compare their process with the original (wrong) process. It makes it more obvious where the original problem solver went wrong.

The written explanation can be the most difficult part. When I started doing problems like this, students would explain, in an addition problem, “I started in the ones and added 8+7. I left the 5 in the one’s place and regrouped the 1.” While technically that is true and we as teachers understand, that’s not showing an understanding. That is why practicing the structure of Claim, Evidence, and Reasoning (CER) is so important.

Claim: Ms. N. did not draw a quadrilateral.
Evidence: The student example with explanation.
Reasoning: Definition of a polygon and Ms. N’s error.

Finding Problems

One of the easiest ways to collect incorrect problems is from your class. Whether you use exit tickets or collect information from the day’s lesson, you have a plethora of options. When using student errors, it’s advisable to use a common mistake by many students. Done early, this can correct any misconceptions before they become habits. Ligia suggests using


Teachers and students alike enjoy this math EduProtocol. Students find it ‘fun’ to find the mistakes. Teachers report that it takes little time to begin implementing in their classes. Doing this a few times a week can really improve understanding. Let’s face it, students LOVE to point out teachers’ mistakes.

If you use this, I would love to hear how it went. What changes did you make? How have your students improved with error analysis?

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