Thought Bubbles

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SWBAT determine if an explanation of equality is true or false.

Big Idea

Students apply what they know about the equal sign to "critique the reasoning of others" in this closing lesson!

Hook and Objective

6 minutes


We have looked at the equal sign so many times. Today we are going to analyze someone’s thinking and decide if they are correct or not! We are going to pretend we are reading someone’s mind.


Great thinkers and mathematicians have to explain their thinking and be able to determine if they agree or disagree with someone else’s thinking.

Objective:  Is this true or false? What evidence do I have to prove it?

Hook! Get kids excited using the plan of "reading minds"! Watch the VERY fun Magic we cast so that we can see into each other's brains! 


Opening Discussion

15 minutes

Everytime I have someone come up, I am going to cast this spell again and have the kids close their eyes, then when they open their eyes, they’ll see that there is a “thought bubble” by the child’s head that I chose. I’m just going to make a poster board thought bubble. Then we will read the person’s mind!

Thought bubble 1: I am trying to figure out 5+5+2. I think the answer is 10 because 5+5 is equal to 5+5+2.

  • Partner talk: Retell what this person thinks.
  • Whole class vote: Do you agree or disagree with this person’s thinking? Do you think the answer is 10?

We have to be able to prove it one way or another! You are going to prove it and share what you found. This is aligned to MP3, Construct viable arguments and critique the reasoning of others. Students determine if the thinking is correct or not, but they have to back it up with evidence! 

 I’ll have students use white boards/work at desks quickly to solve the initial problem and then figure out if the answer is 10.

I’m going to share an exemplar of how to prove it.

  • This person said 5+5 is equal to 5+5+2. Let’s show that in symbols.

On chart paper: 5+5=5+5+2

Pro Tip! A key part of students solving this correctly is having them draw a line down the middle where the equals sign is. It helps them keep both sides very organized. 

We will solve both sides as a class and determine if it is true or false.

Partner talk: Where did this person go wrong in their thinking?

Student Share

15 minutes

Thought Bubble Spell #2: I am trying to solve 9+6. 9+6 is equal to 10+5. So the answer is 15. This thought bubble helps set students up to think about the concept of "making 10" to solve. This is an explicitly stated strategy in 1.OA.1. Giving kids experiences like this one helps them start with the understanding that those 2 equations are equal. In later units, you will actually model why they are equal using double ten frames.

  • Partner talk: Retell what this person thinks.
  • Whole class vote: Do you agree or disagree with this person’s thinking? Do you think the answer is 8?
  • Reiterate MP3: Can we just say true or false because of what we predict/think? No! We have to always back it up with evidence. We have to solve first, then decide.

Work Time:

Students solve on rug. Remind them before they go of how I set up the exemplar earlier in the lesson with the line down the middle. They can rewrite the story as 9+6=10+5 and then prove it.

Watch the Student Work Time video; students work in their notepads on the rug. I keep a stack of cheap legal pads for each child by the carpet with skinny markers. Sometimes I prefer this over whiteboards-it leads to less erasing and kids LOVE writing in marker! You'll see a variety of strategies that students choose to prove that 10+6=9+5, especially wait for the cool counting strategy you hear in the last couple of seconds!

Student Share: 1 student shares thinking, all other students retell what that person did to solve with partner.

If time, do another one in a similar fashion!

Independent Practice

15 minutes

Students prove if equations are true or false independently. This is another time to hold kids accountable for proving BOTH sides. Students are always constructing viable arguments (MP3) and showing their thinking.

For students who need more intervention, give them the equations with smaller numbers. After they get some practice with the concept of "proving" something true/false, we can up the numbers. For now focus on WHY you would circle true vs. false. 

Independent Practice documents are attached!


5 minutes

Do one more magic spell on the rug!