Acting out Change Unknown Problems

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SWBAT solve change unknown problems using addition or subtraction strategies.

Big Idea

Students act out change unknown problems so that they can see the "action" in the problem.


10 minutes

Today we are going to act out a word problem!   I need a few students to help me out! 

Let’s act out this problem out.

_________ had 67 apples.  He gave a lot of apples to his friends.  Now ____ has 13 apples.  How many apples did _________ give away?

Have students act this out either using cubes, counters, or another small object—students can also use white boards. Either have some students model this problem OR have students work in groups of two and three and then have a few students share out their “story problem”.  

Introduction to New Material

10 minutes

We just had a chance to act out a problem.  Now let’s solve that problem on our white boards:

_________ had 67 apples.  He gave a lot of apples to his friends.  Now ____ has 13 apples.  How many apples did _________ give away?

I allow students 3-5 minutes to solve the problem.  Students can solve the problem by subtracting (67-13= ___  or by adding 13 + _______ = 67.   As long as students are getting an accurate answer, any way of setting up the problem is accurate.   Some students may fall in the pitfall of simply adding 67 + 13—drawing the problem and/or acting it out may help students to fully conceptualize the problem.

Now I want you to show me how you solved the problem.   I ask two or three students to share their strategy, stopping to ask guiding questions as necessary:

1) Why did you choose to add or subtract?

2) How does your number sentence match your story problem?


Guided Practice

10 minutes

Students will work in groups of two to complete and check two problems using a criteria for success.

Criteria for success:

__My number sentence matches the story problem

__My addition or subtraction is accurate (and I have checked my work!)

To make this criteria for success meaningful, we look at two pieces of work from our problem of the day and assess as a class whether the number sentence matches the story problem and whether the addition/ subtraction is accurate.  Evaluating a problem as a whole class enables students to see how the criteria for success works and what excellent work looks like.

Students will work on problem 1 and then will trade papers to check each other’s work.  In order for this activity to be impactful,  I model how  to check someone’s work using the checklist and how to give feedback giving the following sentence starters:

--I liked the way that you…

--Next time, remember to…

I allow students about 10-11 minutes to work on the two problems, check each other’s work, and give feedback.  As students work, I listen to student conversations and where needed, coach students in giving good feedback and/or prompt students who are struggling to solve the problem.   If time permits, I bring the students back together and go over one of the problems

Independent Practice

15 minutes

Independent practice is tiered by student understanding of change unknown problems: 

Group A: In need of intervention

Students in group A will solve change unknown word problems with numbers 30-90. 

Group B: Right on track! 

Students in group B will solve change unknown word problems with numbers 30-150. 

Group C: Extension

Students in group C will solve change unknown word problems with numbers 30-300. 

During independent practice,  I will circulate between the groups, spending the majority of my time with the A group.  


5 minutes

Today we worked on strategies for solving missing part problems.  You are going to show me what you know by working on an exit ticket.

Once they have finished, I go over the exit ticket with the students to reinforce strategies.