Adding & Subtracting Mixed Numbers (Practice - Problem Solving)

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SWBAT solve problems involving addition and subtraction of mixed numbers.

Big Idea

Students put their knowledge of adding and subtracting to use to solve problems.


5 minutes

I ask students to take time to list all of their fraction skills in their math journal.  Throughout this unit, I have consistently revisited the idea of fraction skills as building blocks.  Usually, I list the skills they have been working to master on the board as students share them out loud.  At this time, I shift the ownership from the group to the individual student.  

After a few minutes of listing, I allow time to talk with their group members so they can add more skills that they may have left out.

Launch/Guided Practice

20 minutes

This video clip aligns with my approach when teaching students how to add and subtract fractions. I use it to launch this lesson because it is very thorough, informative, and engaging.  Students are learning to use the iPad app educreations and this also provides a great model of what they can do with this app.

Following the video clip, I ask students to think of a related story problem for each of the equations presented in the clip.  

Two students are chosen to share their story problem and as a class, using interactive modeling, we create bar diagrams to match these situations. (2 and 1/3 + 3 and 3/4= 6 and 1/2)  (4 and 2/4 - 2 and 1/6 = 2 and 1/3)

* My friends and I went to the movies. When we got to our seats we had 4 and 2/3 bags of popcorn.  By the time the previews were over we had eaten 2 and 1/6 bags of popcorn.  How much popcorn did we have to eat during the actual movie?

This provides students with a refresher of the skills they will use to complete the independent practice portion of the lesson.

Independent Practice

20 minutes

Students work in pairs to solve problems involving addition and subtraction of mixed numbers.  I have selected six problems from the text book.  I choose a combination of addition and subtraction problems.  

When solving problems, I expect students to formulate an equation, estimate, draw a bar diagram that matches the equation and then solve.  

To help organize their thinking about this multiple step approach, I provide a handout of an organization tool with each of these sections.  I purposefully only provide one of these organizers on the handout because I want to gradually release this scaffolding.  Students will be expected to use the same formatting for each of the remaining problems, but they will have to use the organizer as a model.

At this point in the unit, students are moving toward independence when working with fractions. While students are working, I circulate around the room to check on their progress and provide support as needed.

Group Share

5 minutes

The students are given a chance to ask questions and also share any mistakes that they made, and what they learned from it.

Here is a summary of some examples of what the students share:

• We had a math argument about an improper fraction.  I learned that I subtracted wrong and so I had to fix my mistake.

• We had a really hard time with one of the problems.  The denominator was 24 and we ended up with so many of them (47) that we kept getting confused.  We kept changing our answers and getting such different things.  It took us a while to finish it, but we PERSEVERED and got through it. (Perseverance is one of our core values, and also a mathematical practice (MP1) in the Common Core State Standards.)

• We got an answer that was nothing like our estimate.  So had to find our mistake.  In the end, we realized that our answer was only including the fractional parts of the mixed numbers.  We didn't add the wholes in too.

Ticket Out

5 minutes

Students reflect on today's task by putting a face on the top right corner of the paper and then, add a caption to explain their choice.

Papers are handed in and I use these to generate a list of students who need more support.